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NEWS
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This document summarizes the most important changes in the current Bro
release. For an exhaustive list of changes, see the ``CHANGES`` file
(note that submodules, such as BroControl and Broccoli, come with
their own ``CHANGES``.)
Bro 2.5
=======
New Dependencies
----------------
- Bro now requires a compiler with C++11 support for building the
source code.
- Bro now requires Python instead of Perl to compile the source code.
- When enabling Broker (which is disabled by default), Bro now requires
version 0.14 of the C++ Actor Framework.
New Functionality
-----------------
- SMB analyzer. This is the rewrite that has been in development for
several years. The scripts are currently not loaded by default and
must be loaded manually by loading policy/protocols/smb. The next
release will load the smb scripts by default.
- Implements SMB1+2.
- Fully integrated with the file analysis framework so that files
transferred over SMB can be analyzed.
- Includes GSSAPI and NTLM analyzer and reimplements the DCE-RPC
analyzer.
- New logs: smb_cmd.log, smb_files.log, smb_mapping.log, ntlm.log,
and dce_rpc.log
- Not every possible SMB command or functionality is implemented, but
generally, file handling should work whenever files are transferred.
Please speak up on the mailing list if there is an obvious oversight.
- Bro now includes the NetControl framework. The framework allows for easy
interaction of Bro with hard- and software switches, firewalls, etc.
New log files: netcontrol.log, netcontrol_catch_release.log,
netcontrol_drop.log, and netcontrol_shunt.log.
- Bro now includes the OpenFlow framework which exposes the data structures
necessary to interface to OpenFlow capable hardware.
- Bro's Intelligence Framework was refactored and new functionality
has been added:
- The framework now supports the new indicator type Intel::SUBNET.
As subnets are matched against seen addresses, the new field 'matched'
in intel.log was introduced to indicate which indicator type(s) caused
the hit.
- The new function remove() allows to delete intelligence items.
- The intel framework now supports expiration of intelligence items.
Expiration can be configured using the new Intel::item_expiration constant
and can be handled by using the item_expired() hook. The new script
do_expire.bro removes expired items.
- The new hook extend_match() allows extending the framework. The new
policy script whitelist.bro uses the hook to implement whitelisting.
- Intel notices are now suppressible and mails for intel notices now
list the identified services as well as the intel source.
- There is a new file entropy analyzer for files.
- Bro now supports the remote framebuffer protocol (RFB) that is used by
VNC servers for remote graphical displays. New log file: rfb.log.
- Bro now supports the Radiotap header for 802.11 frames.
- Bro now has rudimentary IMAP and XMPP analyzers examining the initial
phases of the protocol. Right now these analyzers only identify
STARTTLS sessions, handing them over to TLS analysis. These analyzers
do not yet analyze any further IMAP/XMPP content.
- New funtionality has been added to the SSL/TLS analyzer:
- Bro now supports (draft) TLS 1.3.
- The new event ssl_extension_signature_algorithm() allows access to the
TLS signature_algorithms extension that lists client supported signature
and hash algorithm pairs.
- The new event ssl_extension_key_share gives access to the supported named
groups in TLS 1.3.
- The new event ssl_application_data gives information about application data
that is exchanged before encryption fully starts. This is used to detect
when encryption starts in TLS 1.3.
- Bro now tracks VLAN IDs. To record them inside the connection log,
load protocols/conn/vlan-logging.bro.
- A new dns_CAA_reply() event gives access to DNS Certification Authority
Authorization replies.
- A new per-packet event raw_packet() provides access to layer 2
information. Use with care, generating events per packet is
expensive.
- A new built-in function, decode_base64_conn() for Base64 decoding.
It works like decode_base64() but receives an additional connection
argument that will be used for decoding errors into weird.log
(instead of reporter.log).
- A new get_current_packet_header() bif returns the headers of the current
packet.
- Three new built-in functions for handling set[subnet] and table[subnet]:
- check_subnet(subnet, table) checks if a specific subnet is a member
of a set/table. This is different from the "in" operator, which always
performs a longest prefix match.
- matching_subnets(subnet, table) returns all subnets of the set or table
that contain the given subnet.
- filter_subnet_table(subnet, table) works like matching_subnets, but returns
a table containing all matching entries.
- Several built-in functions for handling IP addresses and subnets were added:
- is_v4_subnet(subnet) checks whether a subnet specification is IPv4.
- is_v6_subnet(subnet) checks whether a subnet specification is IPv6.
- addr_to_subnet(addr) converts an IP address to a /32 subnet.
- subnet_to_addr(subnet) returns the IP address part of a subnet.
- subnet_width(subnet) returns the width of a subnet.
- The IRC analyzer now recognizes StartTLS sessions and enables the SSL
analyzer for them.
- The misc/stats.bro script is now loaded by default and logs more Bro
execution statistics to the stats.log file than it did previously. It
now also uses the standard Bro log format.
- A set of new built-in functions for gathering execution statistics:
get_net_stats(), get_conn_stats(), get_proc_stats(),
get_event_stats(), get_reassembler_stats(), get_dns_stats(),
get_timer_stats(), get_file_analysis_stats(), get_thread_stats(),
get_gap_stats(), get_matcher_stats()
- Two new functions haversine_distance() and haversine_distance_ip()
for calculating geographic distances. The latter function requires that Bro
be built with libgeoip.
- Table expiration timeout expressions are evaluated dynamically as
timestamps are updated.
- The pcap buffer size can be set through the new option Pcap::bufsize.
- Input framework readers stream types Table and Event can now define a custom
event (specified by the new "error_ev" field) to receive error messages
emitted by the input stream. This can, e.g., be used to raise notices in
case errors occur when reading an important input source.
- The logging framework now supports user-defined record separators,
renaming of column names, as well as extension data columns that can
be added to specific or all logfiles (e.g., to add new names).
- The new "bro-config" script can be used to determine the Bro installation
paths.
- New BroControl functionality in aux/broctl:
- There is a new node type "logger" that can be specified in
node.cfg (that file has a commented-out example). The purpose of
this new node type is to receive logs from all nodes in a cluster
in order to reduce the load on the manager node. However, if
there is no "logger" node, then the manager node will handle
logging as usual.
- The post-terminate script will send email if it fails to archive
any log files. These mails can be turned off by changing the
value of the new BroControl option MailArchiveLogFail.
- Added the ability for "broctl deploy" to reload the BroControl
configuration (both broctl.cfg and node.cfg). This happens
automatically if broctl detects any changes to those config files
since the last time the config was loaded. Note that this feature
is relevant only when using the BroControl shell interactively.
- The BroControl plugin API has a new function "broctl_config".
This gives plugin authors the ability to add their own script code
to the autogenerated broctl-config.bro script.
- There is a new BroControl plugin for custom load balancing. This
plugin can be used by setting "lb_method=custom" for your worker
nodes in node.cfg. To support packet source plugins, it allows
configuration of a prefix and suffix for the interface name.
- New Bro plugins in aux/plugins:
- af_packet: Native AF_PACKET support.
- kafka : Log writer interfacing to Kafka.
- myricom: Native Myricom SNF v3 support.
- pf_ring: Native PF_RING support.
- postgresql: A PostgreSQL reader/writer.
- redis: An experimental log writer for Redis.
- tcprs: A TCP-level analyzer detecting retransmissions, reordering, and more.
Changed Functionality
---------------------
- Log changes:
- Connections
The 'history' field gains two new flags: '^' indicates that
Bro heuristically flipped the direction of the connection.
't/T' indicates the first TCP payload retransmission from
originator or responder, respectively.
- Intelligence
New field 'matched' to indicate which indicator type(s) caused the hit.
- DNS
New 'rtt' field to indicate the round trip time between when a
request was sent and when a reply started.
- SMTP
New 'cc' field which includes the 'Cc' header from MIME
messages sent over SMTP.
Changes in 'mailfrom' and 'rcptto' fields to remove some
non-address cruft that will tend to be found. The main
example is the change from ``"<user@domain>"`` to
``"[email protected]"``.
- HTTP
Removed 'filename' field (which was seldomly used).
New 'orig_filenames' and 'resp_filenames' fields which each
contain a vector of filenames seen in entities transferred.
- stats.log
The following fields have been added: active_tcp_conns,
active_udp_conns, active_icmp_conns, tcp_conns, udp_conns,
icmp_conns, timers, active_timers, files, active_files, dns_requests,
active_dns_requests, reassem_tcp_size, reassem_file_size,
reassem_frag_size, reassem_unknown_size.
The following fields have been renamed: lag -> pkt_lag.
The following fields have been removed: pkts_recv.
- The BrokerComm and BrokerStore namespaces were renamed to Broker.
The Broker "print()" function was renamed to Broker::send_print(), and
the "event()" function was renamed to Broker::send_event().
- The constant ``SSH::skip_processing_after_detection`` was removed. The
functionality was replaced by the new constant
``SSH::disable_analyzer_after_detection``.
- The ``net_stats()`` and ``resource_usage()`` functions have been
removed, and their functionality is now provided by the new execution
statistics functions (see above).
- Some script-level identifiers have changed their names:
- snaplen -> Pcap::snaplen
- precompile_pcap_filter() -> Pcap::precompile_pcap_filter()
- install_pcap_filter() -> Pcap::install_pcap_filter()
- pcap_error() -> Pcap::error()
- TCP analysis was changed to process connections without the initial
SYN packet. In the past, connections without a full handshake were
treated as partial, meaning that most application-layer analyzers
would refuse to inspect the payload. Now, Bro will consider these
connections as complete and all analyzers will process them normally.
- The ``policy/misc/capture-loss.bro`` script is now loaded by default.
- The traceroute detection script package ``policy/misc/detect-traceroute``
is no longer loaded by default.
- Changed BroControl functionality in aux/broctl:
- The networks.cfg file now contains private IP space 172.16.0.0/12
by default.
- Upon startup, if broctl can't get IP addresses from the "ifconfig"
command for any reason, then broctl will now also try to use the
"ip" command.
- BroControl will now automatically search the Bro plugin directory
for BroControl plugins (in addition to all the other places where
BroControl searches). This enables automatic loading of
BroControl plugins that are provided by a Bro plugin.
- Changed the default value of the StatusCmdShowAll option so that
the "broctl status" command runs faster. This also means that
there is no longer a "Peers" column in the status output by
default.
- Users can now specify a more granular log expiration interval. The
BroControl option LogExpireInterval can be set to an arbitrary
time interval instead of just an integer number of days. The time
interval is specified as an integer followed by a time unit:
"day", "hr", or "min". For backward compatibility, an integer
value without a time unit is still interpreted as a number of
days.
- Changed the text of crash report emails. Now crash reports tell
the user to forward the mail to the Bro team only when a backtrace
is included in the crash report. If there is no backtrace, then
the crash report includes instructions on how to get backtraces
included in future crash reports.
- There is a new option SitePolicyScripts that replaces SitePolicyStandalone
(the old option is still available, but will be removed in the next
release).
Removed Functionality
---------------------
- The app-stats scripts have been removed because they weren't
being maintained and they were becoming inaccurate (as a result, the
app_stats.log is also gone). They were also prone to needing more regular
updates as the internet changed and will likely be more relevant if
maintained externally.
- The event ack_above_hole() has been removed, as it was a subset
of content_gap() and led to plenty of noise.
- The command line options ``--analyze``, ``--set-seed``, and
``--md5-hashkey`` have been removed.
- The packaging scripts pkg/make-\*-packages are gone. They aren't
used anymore for the binary Bro packages that the project
distributes; haven't been supported in a while; and have
problems.
Deprecated Functionality
------------------------
- The built-in functions decode_base64_custom() and
encode_base64_custom() are no longer needed and will be removed
in the future. Their functionality is now provided directly by
decode_base64() and encode_base64(), which take an optional
parameter to change the Base64 alphabet.
Bro 2.4
=======
New Functionality
-----------------
- Bro now has support for external plugins that can extend its core
functionality, like protocol/file analysis, via shared libraries.
Plugins can be developed and distributed externally, and will be
pulled in dynamically at startup (the environment variables
BRO_PLUGIN_PATH and BRO_PLUGIN_ACTIVATE can be used to specify the
locations and names of plugins to activate). Currently, a plugin
can provide custom protocol analyzers, file analyzers, log writers,
input readers, packet sources and dumpers, and new built-in functions.
A plugin can furthermore hook into Bro's processing at a number of
places to add custom logic.
See https://www.bro.org/sphinx-git/devel/plugins.html for more
information on writing plugins.
- Bro now has support for the MySQL wire protocol. Activity gets
logged into mysql.log.
- Bro now parses DTLS traffic. Activity gets logged into ssl.log.
- Bro now has support for the Kerberos KRB5 protocol over TCP and
UDP. Activity gets logged into kerberos.log.
- Bro now has an RDP analyzer. Activity gets logged into rdp.log.
- Bro now has a file analyzer for Portable Executables. Activity gets
logged into pe.log.
- Bro now has support for the SIP protocol over UDP. Activity gets
logged into sip.log.
- Bro now features a completely rewritten, enhanced SSH analyzer. The
new analyzer is able to determine if logins failed or succeeded in
most circumstances, logs a lot more more information about SSH
sessions, supports v1, and introduces the intelligence type
``Intel::PUBKEY_HASH`` and location ``SSH::IN_SERVER_HOST_KEY``. The
analayzer also generates a set of additional events
(``ssh_auth_successful``, ``ssh_auth_failed``, ``ssh_auth_attempted``,
``ssh_auth_result``, ``ssh_capabilities``, ``ssh2_server_host_key``,
``ssh1_server_host_key``, ``ssh_encrypted_packet``,
``ssh2_dh_server_params``, ``ssh2_gss_error``, ``ssh2_ecc_key``). See
next section for incompatible SSH changes.
- Bro's file analysis now supports reassembly of files that are not
transferred/seen sequentially. The default file reassembly buffer
size is set with the ``Files::reassembly_buffer_size`` variable.
- Bro's file type identification has been greatly improved (new file types,
bug fixes, and performance improvements).
- Bro's scripting language now has a ``while`` statement::
while ( i < 5 )
print ++i;
``next`` and ``break`` can be used inside the loop's body just like
with ``for`` loops.
- Bro now integrates Broker, a new communication library. See
aux/broker/README for more information on Broker, and
doc/frameworks/broker.rst for the corresponding Bro script API.
With Broker, Bro has the similar capabilities of exchanging events and
logs with remote peers (either another Bro process or some other
application that uses Broker). It also includes a key-value store
API that can be used to share state between peers and optionally
allow data to persist on disk for longer-term storage.
Broker support is by default off for now; it can be enabled at
configure time with --enable-broker. It requires CAF version 0.13+
(https://github.com/actor-framework/actor-framework) as well as a
C++11 compiler (e.g. GCC 4.8+ or Clang 3.3+).
Broker will become a mandatory dependency in future Bro versions and
replace the current communication and serialization system.
- Add --enable-c++11 configure flag to compile Bro's source code in
C++11 mode with a corresponding compiler. Note that 2.4 will be the
last version of Bro that compiles without C++11 support.
- The SSL analysis now alerts when encountering SSL connections with
old protocol versions or unsafe cipher suites. It also gained
extended reporting of weak keys, caching of already validated
certificates, and full support for TLS record defragmentation. SSL generally
became much more robust and added several fields to ssl.log (while
removing some others).
- A new icmp_sent_payload event provides access to ICMP payload.
- The input framework's raw reader now supports seeking by adding an
option "offset" to the config map. Positive offsets are interpreted
to be from the beginning of the file, negative from the end of the
file (-1 is end of file).
- One can now raise events when a connection crosses a given size
threshold in terms of packets or bytes. The primary API for that
functionality is in base/protocols/conn/thresholds.bro.
- There is a new command-line option -Q/--time that prints Bro's execution
time and memory usage to stderr.
- BroControl now has a new command "deploy" which is equivalent to running
the "check", "install", "stop", and "start" commands (in that order).
- BroControl now has a new option "StatusCmdShowAll" that controls whether
or not the broctl "status" command gathers all of the status information.
This option can be used to make the "status" command run significantly
faster (in this case, the "Peers" column will not be shown in the output).
- BroControl now has a new option "StatsLogEnable" that controls whether
or not broctl will record information to the "stats.log" file. This option
can be used to make the "broctl cron" command run slightly faster (in this
case, "broctl cron" will also no longer send email about not seeing any
packets on the monitoring interfaces).
- BroControl now has a new option "MailHostUpDown" which controls whether or
not the "broctl cron" command will send email when it notices that a host
in the cluster is up or down.
- BroControl now has a new option "CommandTimeout" which specifies the number
of seconds to wait for a command that broctl ran to return results.
Changed Functionality
---------------------
- bro-cut has been rewritten in C, and is hence much faster.
- File analysis
* Removed ``fa_file`` record's ``mime_type`` and ``mime_types``
fields. The event ``file_sniff`` has been added which provides
the same information. The ``mime_type`` field of ``Files::Info``
also still has this info.
* The earliest point that new mime type information is available is
in the ``file_sniff`` event which comes after the ``file_new`` and
``file_over_new_connection`` events. Scripts which inspected mime
type info within those events will need to be adapted. (Note: for
users that worked w/ versions of Bro from git, for a while there was
also an event called ``file_mime_type`` which is now replaced with
the ``file_sniff`` event).
* Removed ``Files::add_analyzers_for_mime_type`` function.
* Removed ``offset`` parameter of the ``file_extraction_limit``
event. Since file extraction now internally depends on file
reassembly for non-sequential files, "offset" can be obtained
with other information already available -- adding together
``seen_bytes`` and ``missed_bytes`` fields of the ``fa_file``
record gives how many bytes have been written so far (i.e.
the "offset").
- The SSH changes come with a few incompatibilities. The following
events have been renamed:
* ``SSH::heuristic_failed_login`` to ``ssh_auth_failed``
* ``SSH::heuristic_successful_login`` to ``ssh_auth_successful``
The ``SSH::Info`` status field has been removed and replaced with
the ``auth_success`` field. This field has been changed from a
string that was previously ``success``, ``failure`` or
``undetermined`` to a boolean. a boolean that is ``T``, ``F``, or
unset.
- The has_valid_octets function now uses a string_vec parameter instead of
string_array.
- conn.log gained a new field local_resp that works like local_orig,
just for the responder address of the connection.
- GRE tunnels are now identified as ``Tunnel::GRE`` instead of
``Tunnel::IP``.
- The default name for extracted files changed from extract-protocol-id
to extract-timestamp-protocol-id.
- The weird named "unmatched_HTTP_reply" has been removed since it can
be detected at the script-layer and is handled correctly by the
default HTTP scripts.
- When adding a logging filter to a stream, the filter can now inherit
a default ``path`` field from the associated ``Log::Stream`` record.
- When adding a logging filter to a stream, the
``Log::default_path_func`` is now only automatically added to the
filter if it has neither a ``path`` nor a ``path_func`` already
explicitly set. Before, the default path function would always be set
for all filters which didn't specify their own ``path_func``.
- BroControl now establishes only one ssh connection from the manager to
each remote host in a cluster configuration (previously, there would be
one ssh connection per remote Bro process).
- BroControl now uses SQLite to record state information instead of a
plain text file (the file "spool/broctl.dat" is no longer used).
On FreeBSD, this means that there is a new dependency on the package
"py27-sqlite3".
- BroControl now records the expected running state of each Bro node right
before each start or stop. The "broctl cron" command uses this info to
either start or stop Bro nodes as needed so that the actual state matches
the expected state (previously, "broctl cron" could only start nodes in
the "crashed" state, and could never stop a node).
- BroControl now sends all normal command output (i.e., not error messages)
to stdout. Error messages are still sent to stderr, however.
- The capability of processing NetFlow input has been removed for the
time being. Therefore, the -y/--flowfile and -Y/--netflow command-line
options have been removed, and the netflow_v5_header and netflow_v5_record
events have been removed.
- The -D/--dfa-size command-line option has been removed.
- The -L/--rule-benchmark command-line option has been removed.
- The -O/--optimize command-line option has been removed.
- The deprecated fields "hot" and "addl" have been removed from the
connection record. Likewise, the functions append_addl() and
append_addl_marker() have been removed.
- Log files now escape non-printable characters consistently as "\xXX'.
Furthermore, backslashes are escaped as "\\", making the
representation fully reversible.
Deprecated Functionality
------------------------
- The split* family of functions are to be replaced with alternate
versions that return a vector of strings rather than a table of
strings. This also allows deprecation for some related string
concatenation/extraction functions. Note that the new functions use
0-based indexing, rather than 1-based.
The full list of now deprecated functions is:
* split: use split_string instead.
* split1: use split_string1 instead.
* split_all: use split_string_all instead.
* split_n: use split_string_n instead.
* cat_string_array: see join_string_vec instead.
* cat_string_array_n: see join_string_vec instead.
* join_string_array: see join_string_vec instead.
* sort_string_array: use sort instead.
* find_ip_addresses: use extract_ip_addresses instead.
Bro 2.3
=======
Dependencies
------------
- Libmagic is no longer a dependency.
New Functionality
-----------------
- Support for GRE tunnel decapsulation, including enhanced GRE
headers. GRE tunnels are treated just like IP-in-IP tunnels by
parsing past the GRE header in between the delivery and payload IP
packets.
- The DNS analyzer now actually generates the dns_SRV_reply() event.
It had been documented before, yet was never raised.
- Bro now uses "file magic signatures" to identify file types. These
are defined via two new constructs in the signature rule parsing
grammar: "file-magic" gives a regular expression to match against,
and "file-mime" gives the MIME type string of content that matches
the magic and an optional strength value for the match. (See also
"Changed Functionality" below for changes due to switching from
using libmagic to such signatures.)
- A new built-in function, "file_magic", can be used to get all file
magic matches and their corresponding strength against a given chunk
of data.
- The SSL analyzer now supports heartbeats as well as a few
extensions, including server_name, alpn, and ec-curves.
- The SSL analyzer comes with Heartbleed detector script in
protocols/ssl/heartbleed.bro. Note that loading this script changes
the default value of "SSL::disable_analyzer_after_detection" from true
to false to prevent encrypted heartbeats from being ignored.
- StartTLS is now supported for SMTP and POP3.
- The X509 analyzer can now perform OSCP validation.
- Bro now has analyzers for SNMP and Radius, which produce corresponding
snmp.log and radius.log output (as well as various events of course).
- BroControl has a new option "BroPort" which allows a user to specify
the starting port number for Bro.
- BroControl has a new option "StatsLogExpireInterval" which allows a
user to specify when entries in the stats.log file expire.
- BroControl has a new option "PFRINGClusterType" which allows a user
to specify a PF_RING cluster type.
- BroControl now supports PF_RING+DNA. There is also a new option
"PFRINGFirstAppInstance" that allows a user to specify the starting
application instance number for processes running on a DNA cluster.
See the BroControl documentation for more details.
- BroControl now warns a user to run "broctl install" if Bro has
been upgraded or if the broctl or node configuration has changed
since the most recent install.
Changed Functionality
---------------------
- string slices now exclude the end index (e.g., "123"[1:2] returns
"2"). Generally, Bro's string slices now behave similar to Python.
- ssl_client_hello() now receives a vector of ciphers, instead of a
set, to preserve their order.
- Notice::end_suppression() has been removed.
- Bro now parses X.509 extensions headers and, as a result, the
corresponding event got a new signature:
event x509_extension(c: connection, is_orig: bool, cert: X509, ext: X509_extension_info);
- In addition, there are several new, more specialized events for a
number of x509 extensions.
- Generally, all x509 events and handling functions have changed their
signatures.
- X509 certificate verification now returns the complete certificate
chain that was used for verification.
- Bro no longer special-cases SYN/FIN/RST-filtered traces by not
reporting missing data. Instead, if Bro never sees any data segments
for analyzed TCP connections, the new
base/misc/find-filtered-trace.bro script will log a warning in
reporter.log and to stderr. The old behavior can be reverted by
redef'ing "detect_filtered_trace".
- We have removed the packet sorter component.
- Bro no longer uses libmagic to identify file types but instead now
comes with its own signature library (which initially is still
derived from libmagic's database). This leads to a number of further
changes with regards to MIME types:
* The second parameter of the "identify_data" built-in function
can no longer be used to get verbose file type descriptions,
though it can still be used to get the strongest matching file
magic signature.
* The "file_transferred" event's "descr" parameter no longer
contains verbose file type descriptions.
* The BROMAGIC environment variable no longer changes any behavior
in Bro as magic databases are no longer used/installed.
* Removed "binary" and "octet-stream" mime type detections. They
don't provide any more information than an uninitialized
mime_type field.
* The "fa_file" record now contains a "mime_types" field that
contains all magic signatures that matched the file content
(where the "mime_type" field is just a shortcut for the
strongest match).
- dns_TXT_reply() now supports more than one string entry by receiving
a vector of strings.
- BroControl now runs the "exec" and "df" broctl commands only once
per host, instead of once per Bro node. The output of these
commands has been changed slightly to include both the host and
node names.
- Several performance improvements were made. Particular emphasis
was put on the File Analysis system, which generally will now emit
far fewer file handle request events due to protocol analyzers now
caching that information internally.
Bro 2.2
=======
New Functionality
-----------------
- A completely overhauled intelligence framework for consuming
external intelligence data. It provides an abstracted mechanism
for feeding data into the framework to be matched against the
data available. It also provides a function named ``Intel::match``
which makes any hits on intelligence data available to the
scripting language.
Using input framework, the intel framework can load data from
text files. It can also update and add data if changes are
made to the file being monitored. Files to monitor for
intelligence can be provided by redef-ing the
``Intel::read_files`` variable.
The intel framework is cluster-ready. On a cluster, the
manager is the only node that needs to load in data from disk,
the cluster support will distribute the data across a cluster
automatically.
Scripts are provided at ``policy/frameworks/intel/seen`` that
provide a broad set of sources of data to feed into the intel
framwork to be matched.
- A new file analysis framework moves most of the processing of file
content from script-land into the core, where it belongs. See
``doc/file-analysis.rst``, or the online documentation, for more
information.
Much of this is an internal change, but the framework also comes
with the following user-visible functionality (some of that was
already available before but is done differently, and more
efficiently, now):
- HTTP:
* Identify MIME type of messages.
* Extract messages to disk.
* Compute MD5 for messages.
- SMTP:
* Identify MIME type of messages.
* Extract messages to disk.
* Compute MD5 for messages.
* Provide access to start of entity data.
- FTP data transfers:
* Identify MIME types of data.
* Record to disk.
- IRC DCC transfers: Record to disk.
- Support for analyzing data transferred via HTTP range requests.
- A binary input reader interfaces the input framework with the
file analysis, allowing to inject files on disk into Bro's
content processing.
- A new framework for computing a wide array of summary statistics,
such as counters and thresholds checks, standard deviation and mean,
set cardinality, top K, and more. The framework operates in
real-time, independent of the underlying data, and can aggregate
information from many independent monitoring points (including
clusters). It provides a transparent, easy-to-use user interface,
and can optionally deploy a set of probabilistic data structures for
memory-efficient operation. The framework is located in
``scripts/base/frameworks/sumstats``.
A number of new applications now ship with Bro that are built on top
of the summary statistics framework:
* Scan detection: Detectors for port and address scans. See
``policy/misc/scan.bro`` (these scan detectors used to exist in
Bro versions <2.0; it's now back, but quite different).
* Tracerouter detector: ``policy/misc/detect-traceroute.bro``
* Web application detection/measurement:
``policy/misc/app-stats/*``
* FTP and SSH brute-forcing detector:
``policy/protocols/ftp/detect-bruteforcing.bro``,
``policy/protocols/ssh/detect-bruteforcing.bro``
* HTTP-based SQL injection detector:
``policy/protocols/http/detect-sqli.bro`` (existed before, but
now ported to the new framework)
- GridFTP support. This is an extension to the standard FTP analyzer
and includes:
- An analyzer for the GSI mechanism of GSSAPI FTP AUTH method.
GSI authentication involves an encoded TLS/SSL handshake over
the FTP control session. For FTP sessions that attempt GSI
authentication, the ``service`` field of the connection log
will include ``gridftp`` (as well as also ``ftp`` and
``ssl``).
- An example of a GridFTP data channel detection script. It
relies on the heuristics of GridFTP data channels commonly
default to SSL mutual authentication with a NULL bulk cipher
and that they usually transfer large datasets (default
threshold of script is 1 GB). For identified GridFTP data
channels, the ``services`` fields of the connection log will
include ``gridftp-data``.
- Modbus and DNP3 support. Script-level support is only basic at this
point but see ``src/analyzer/protocol/{modbus,dnp3}/events.bif``, or
the online documentation, for the events Bro generates. For Modbus,
there are also some example policies in
``policy/protocols/modbus/*``.
- The documentation now includes a new introduction to writing Bro
scripts. See ``doc/scripting/index.rst`` or, much better, the online
version. There's also the beginning of a chapter on "Using Bro" in
``doc/using/index.rst``.
- GPRS Tunnelling Protocol (GTPv1) decapsulation.
- The scripting language now provide "hooks", a new flavor of
functions that share characteristics of both standard functions and
events. They are like events in that multiple bodies can be defined
for the same hook identifier. They are more like functions in the
way they are invoked/called, because, unlike events, their execution
is immediate and they do not get scheduled through an event queue.
Also, a unique feature of a hook is that a given hook handler body
can short-circuit the execution of remaining hook handlers simply by
exiting from the body as a result of a ``break`` statement (as
opposed to a ``return`` or just reaching the end of the body). See
``doc/scripts/builtins.rst``, or the online documentation, for more
informatin.
- Bro's language now has a working ``switch`` statement that generally
behaves like C-style switches (except that case labels can be
comprised of multiple literal constants delimited by commas). Only
atomic types are allowed for now. Case label bodies that don't
execute a ``return`` or ``break`` statement will fall through to
subsequent cases. A ``default`` case label is supported.
- Bro's language now has a new set of types ``opaque of X``. Opaque
values can be passed around like other values but they can only be
manipulated with BiF functions, not with other operators. Currently,
the following opaque types are supported::
opaque of md5
opaque of sha1
opaque of sha256
opaque of cardinality
opaque of topk
opaque of bloomfilter
These go along with the corrsponding BiF functions ``md5_*``,
``sha1_*``, ``sha256_*``, ``entropy_*``, etc. . Note that where
these functions existed before, they have changed their signatures
to work with opaques types rather than global state.
- The scripting language now supports constructing sets, tables,
vectors, and records by name::
type MyRecordType: record {
c: count;
s: string &optional;
};
global r: MyRecordType = record($c = 7);
type MySet: set[MyRec];
global s = MySet([$c=1], [$c=2]);
- Strings now support the subscript operator to extract individual
characters and substrings (e.g., ``s[4]``, ``s[1:5]``). The index
expression can take up to two indices for the start and end index of
the substring to return (e.g. ``mystring[1:3]``).
- Functions now support default parameters, e.g.::
global foo: function(s: string, t: string &default="abc", u: count &default=0);
- Scripts can now use two new "magic constants" ``@DIR`` and
``@FILENAME`` that expand to the directory path of the current
script and just the script file name without path, respectively.
- ``ssl.log`` now also records the subject client and issuer
certificates.
- The ASCII writer can now output CSV files on a per filter basis.
- New SQLite reader and writer plugins for the logging framework allow
to read/write persistent data from on disk SQLite databases.
- A new packet filter framework supports BPF-based load-balancing,
shunting, and sampling; plus plugin support to customize filters
dynamically.
- Bro now provides Bloom filters of two kinds: basic Bloom filters
supporting membership tests, and counting Bloom filters that track
the frequency of elements. The corresponding functions are::
bloomfilter_basic_init(fp: double, capacity: count, name: string &default=""): opaque of bloomfilter
bloomfilter_basic_init2(k: count, cells: count, name: string &default=""): opaque of bloomfilter
bloomfilter_counting_init(k: count, cells: count, max: count, name: string &default=""): opaque of bloomfilter
bloomfilter_add(bf: opaque of bloomfilter, x: any)
bloomfilter_lookup(bf: opaque of bloomfilter, x: any): count
bloomfilter_merge(bf1: opaque of bloomfilter, bf2: opaque of bloomfilter): opaque of bloomfilter
bloomfilter_clear(bf: opaque of bloomfilter)
See ``src/probabilistic/bloom-filter.bif``, or the online
documentation, for full documentation.
- Bro now provides a probabilistic data structure for computing
"top k" elements. The corresponding functions are::
topk_init(size: count): opaque of topk
topk_add(handle: opaque of topk, value: any)
topk_get_top(handle: opaque of topk, k: count)
topk_count(handle: opaque of topk, value: any): count
topk_epsilon(handle: opaque of topk, value: any): count
topk_size(handle: opaque of topk): count
topk_sum(handle: opaque of topk): count
topk_merge(handle1: opaque of topk, handle2: opaque of topk)
topk_merge_prune(handle1: opaque of topk, handle2: opaque of topk)
See ``src/probabilistic/top-k.bif``, or the online documentation,
for full documentation.
- Bro now provides a probabilistic data structure for computing set
cardinality, using the HyperLogLog algorithm. The corresponding
functions are::
hll_cardinality_init(err: double, confidence: double): opaque of cardinality
hll_cardinality_add(handle: opaque of cardinality, elem: any): bool
hll_cardinality_merge_into(handle1: opaque of cardinality, handle2: opaque of cardinality): bool
hll_cardinality_estimate(handle: opaque of cardinality): double
hll_cardinality_copy(handle: opaque of cardinality): opaque of cardinality
See ``src/probabilistic/cardinality-counter.bif``, or the online
documentation, for full documentation.
- ``base/utils/exec.bro`` provides a module to start external
processes asynchronously and retrieve their output on termination.
``base/utils/dir.bro`` uses it to monitor a directory for changes,
and ``base/utils/active-http.bro`` for providing an interface for