base/frameworks/notice/main.bro

GLOBAL

Notice

This is the notice framework which enables Bro to “notice” things which are odd or potentially bad. Decisions of the meaning of various notices need to be done per site because Bro does not ship with assumptions about what is bad activity for sites. More extensive documentation about using the notice framework can be found in Notice Framework.

Namespaces:GLOBAL, Notice Imports:base/frameworks/cluster Source File:/scripts/base/frameworks/notice/main.bro

Summary

Runtime Options

Notice::alarmed_types: set &redef	Alarmed notice types.
Notice::default_suppression_interval: interval &redef	The notice framework is able to do automatic notice suppression by utilizing the identifier field in Notice::Info records.
Notice::emailed_types: set &redef	Emailed notice types.
Notice::ignored_types: set &redef	Ignored notice types.
Notice::mail_from: string &redef	Address that emails will be from.
Notice::mail_subject_prefix: string &redef	Text string prefixed to the subject of all emails sent out.
Notice::not_suppressed_types: set &redef	Types that should be suppressed for the default suppression interval.
Notice::reply_to: string &redef	Reply-to address used in outbound email.
Notice::sendmail: string &redef	Local system sendmail program.

Redefinable Options

Notice::mail_dest: string &redef	Email address to send notices with the Notice::ACTION_EMAIL action or to send bulk alarm logs on rotation with Notice::ACTION_ALARM.
Notice::max_email_delay: interval &redef	The maximum amount of time a plugin can delay email from being sent.
Notice::type_suppression_intervals: table &redef	This table can be used as a shorthand way to modify suppression intervals for entire notice types.

Types

Notice::Action: enum	These are values representing actions that can be taken with notices.
Notice::ActionSet: set	Type that represents a set of actions.
Notice::FileInfo: record	Contains a portion of fa_file that’s also contained in Notice::Info.
Notice::Info: record	The record type that is used for representing and logging notices.
Notice::Type: enum	Scripts creating new notices need to redef this enum to add their own specific notice types which would then get used when they call the NOTICE function.

Redefinitions

Log::ID: enum

Events

Notice::begin_suppression: event	This event is generated when a notice begins to be suppressed.
Notice::cluster_notice: event	This is the event used to transport notices on the cluster.
Notice::log_notice: event	This event can be handled to access the Notice::Info record as it is sent on to the logging framework.
Notice::suppressed: event	This event is generated on each occurrence of an event being suppressed.

Hooks

Notice::notice: hook	This is the event that is called as the entry point to the notice framework by the global NOTICE function.
Notice::policy: hook	The hook to modify notice handling.

Functions

NOTICE: function
Notice::create_file_info: function	Creates a record containing a subset of a full fa_file record.
Notice::email_headers: function	Constructs mail headers to which an email body can be appended for sending with sendmail.
Notice::email_notice_to: function	Call this function to send a notice in an email.
Notice::internal_NOTICE: function	This is an internal wrapper for the global NOTICE function; disregard.
Notice::is_being_suppressed: function	A function to determine if an event is supposed to be suppressed.
Notice::log_mailing_postprocessor: function	A log postprocessing function that implements emailing the contents of a log upon rotation to any configured Notice::mail_dest.
Notice::populate_file_info: function	Populates file-related fields in a notice info record.
Notice::populate_file_info2: function	Populates file-related fields in a notice info record.

Detailed Interface

Runtime Options

Notice::alarmed_types

Type:set [Notice::Type] Attributes:&redef Default:{}

Alarmed notice types.

Notice::default_suppression_interval

Type:interval Attributes:&redef Default:1.0 hr

The notice framework is able to do automatic notice suppression by utilizing the identifier field in Notice::Info records. Set this to “0secs” to completely disable automated notice suppression.

Notice::emailed_types

Type:set [Notice::Type] Attributes:&redef Default:{}

Emailed notice types.

Notice::ignored_types

Type:set [Notice::Type] Attributes:&redef Default:{}

Ignored notice types.

Notice::mail_from

Type:string Attributes:&redef Default:"Big Brother <bro@localhost>"

Address that emails will be from.

Note that this is overridden by the BroControl MailFrom option.

Notice::mail_subject_prefix

Type:string Attributes:&redef Default:"[Bro]"

Text string prefixed to the subject of all emails sent out.

Note that this is overridden by the BroControl MailSubjectPrefix option.

Notice::not_suppressed_types

Type:set [Notice::Type] Attributes:&redef Default:{}

Types that should be suppressed for the default suppression interval.

Notice::reply_to

Type:string Attributes:&redef Default:""

Reply-to address used in outbound email.

Notice::sendmail

Type:string Attributes:&redef Default:"/usr/sbin/sendmail"

Local system sendmail program.

Note that this is overridden by the BroControl SendMail option.

Redefinable Options

Notice::mail_dest

Type:string Attributes:&redef Default:""

Email address to send notices with the Notice::ACTION_EMAIL action or to send bulk alarm logs on rotation with Notice::ACTION_ALARM.

Note that this is overridden by the BroControl MailTo option.

Notice::max_email_delay

Type:interval Attributes:&redef Default:15.0 secs

The maximum amount of time a plugin can delay email from being sent.

Notice::type_suppression_intervals

Type:table [Notice::Type] of interval Attributes:&redef Default:{}

This table can be used as a shorthand way to modify suppression intervals for entire notice types.

Types

Notice::Action

Type:

enum

Notice::ACTION_NONE

Indicates that there is no action to be taken.

Notice::ACTION_LOG

Indicates that the notice should be sent to the notice logging stream.

Notice::ACTION_EMAIL

Indicates that the notice should be sent to the email address(es) configured in the Notice::mail_dest variable.

Notice::ACTION_ALARM

Indicates that the notice should be alarmed. A readable ASCII version of the alarm log is emailed in bulk to the address(es) configured in Notice::mail_dest.

Notice::ACTION_DROP

(present if base/frameworks/notice/actions/drop.bro is loaded)

Drops the address via NetControl::drop_address_catch_release.

Notice::ACTION_EMAIL_ADMIN

(present if base/frameworks/notice/actions/email_admin.bro is loaded)

Indicate that the generated email should be addressed to the appropriate email addresses as found by the Site::get_emails function based on the relevant address or addresses indicated in the notice.

Notice::ACTION_PAGE

(present if base/frameworks/notice/actions/page.bro is loaded)

Indicates that the notice should be sent to the pager email address configured in the Notice::mail_page_dest variable.

Notice::ACTION_ADD_GEODATA

(present if base/frameworks/notice/actions/add-geodata.bro is loaded)

Indicates that the notice should have geodata added for the “remote” host. Site::local_nets must be defined in order for this to work.

These are values representing actions that can be taken with notices.

Notice::ActionSet

Type:set [Notice::Action]

Type that represents a set of actions.

Notice::FileInfo

Type:

record

fuid: string

File UID.

desc: string

File description from e.g. Files::describe.

mime: string &optional

Strongest mime type match for file.

cid: conn_id &optional

Connection tuple over which file is sent.

cuid: string &optional

Connection UID over which file is sent.

Contains a portion of fa_file that’s also contained in Notice::Info.

Notice::Info

Type:

record

ts: time &log &optional

An absolute time indicating when the notice occurred, defaults to the current network time.

uid: string &log &optional

A connection UID which uniquely identifies the endpoints concerned with the notice.

id: conn_id &log &optional

A connection 4-tuple identifying the endpoints concerned with the notice.

conn: connection &optional

A shorthand way of giving the uid and id to a notice. The reference to the actual connection will be deleted after applying the notice policy.

iconn: icmp_conn &optional

A shorthand way of giving the uid and id to a notice. The reference to the actual connection will be deleted after applying the notice policy.

f: fa_file &optional

A file record if the notice is related to a file. The reference to the actual fa_file record will be deleted after applying the notice policy.

fuid: string &log &optional

A file unique ID if this notice is related to a file. If the f field is provided, this will be automatically filled out.

file_mime_type: string &log &optional

A mime type if the notice is related to a file. If the f field is provided, this will be automatically filled out.

file_desc: string &log &optional

Frequently files can be “described” to give a bit more context. This field will typically be automatically filled out from an fa_file record. For example, if a notice was related to a file over HTTP, the URL of the request would be shown.

proto: transport_proto &log &optional

The transport protocol. Filled automatically when either conn, iconn or p is specified.

note: Notice::Type &log

The Notice::Type of the notice.

msg: string &log &optional

The human readable message for the notice.

sub: string &log &optional

The human readable sub-message.

src: addr &log &optional

Source address, if we don’t have a conn_id.

dst: addr &log &optional

Destination address.

p: port &log &optional

Associated port, if we don’t have a conn_id.

n: count &log &optional

Associated count, or perhaps a status code.

peer_name: string &optional

Name of remote peer that raised this notice.

peer_descr: string &log &optional

Textual description for the peer that raised this notice, including name, host address and port.

actions: Notice::ActionSet &log &default = {  } &optional

The actions which have been applied to this notice.

email_body_sections: vector of string &optional

By adding chunks of text into this element, other scripts can expand on notices that are being emailed. The normal way to add text is to extend the vector by handling the Notice::notice event and modifying the notice in place.

email_delay_tokens: set [string] &optional

Adding a string “token” to this set will cause the notice framework’s built-in emailing functionality to delay sending the email until either the token has been removed or the email has been delayed for Notice::max_email_delay.

identifier: string &optional

This field is to be provided when a notice is generated for the purpose of deduplicating notices. The identifier string should be unique for a single instance of the notice. This field should be filled out in almost all cases when generating notices to define when a notice is conceptually a duplicate of a previous notice.

For example, an SSL certificate that is going to expire soon should always have the same identifier no matter the client IP address that connected and resulted in the certificate being exposed. In this case, the resp_h, resp_p, and hash of the certificate would be used to create this value. The hash of the cert is included because servers can return multiple certificates on the same port.

Another example might be a host downloading a file which triggered a notice because the MD5 sum of the file it downloaded was known by some set of intelligence. In that case, the orig_h (client) and MD5 sum would be used in this field to dedup because if the same file is downloaded over and over again you really only want to know about it a single time. This makes it possible to send those notices to email without worrying so much about sending thousands of emails.

suppress_for: interval &log &default = Notice::default_suppression_interval &optional

This field indicates the length of time that this unique notice should be suppressed.

dropped: bool &log &default = F &optional

(present if base/frameworks/notice/actions/drop.bro is loaded)

Indicate if the $src IP address was dropped and denied network access.

remote_location: geo_location &log &optional

(present if base/frameworks/notice/actions/add-geodata.bro is loaded)

If GeoIP support is built in, notices can have geographic information attached to them.

The record type that is used for representing and logging notices.

Notice::Type

Type:

enum

Notice::Tally

Notice reporting a count of how often a notice occurred.

Weird::Activity

(present if base/frameworks/notice/weird.bro is loaded)

Generic unusual but notice-worthy weird activity.

Signatures::Sensitive_Signature

(present if base/frameworks/signatures/main.bro is loaded)

Generic notice type for notice-worthy signature matches.

Signatures::Multiple_Signatures

(present if base/frameworks/signatures/main.bro is loaded)

Host has triggered many signatures on the same host. The number of signatures is defined by the Signatures::vert_scan_thresholds variable.

Signatures::Multiple_Sig_Responders

(present if base/frameworks/signatures/main.bro is loaded)

Host has triggered the same signature on multiple hosts as defined by the Signatures::horiz_scan_thresholds variable.

Signatures::Count_Signature

(present if base/frameworks/signatures/main.bro is loaded)

The same signature has triggered multiple times for a host. The number of times the signature has been triggered is defined by the Signatures::count_thresholds variable. To generate this notice, the Signatures::SIG_COUNT_PER_RESP action must be set for the signature.

Signatures::Signature_Summary

(present if base/frameworks/signatures/main.bro is loaded)

Summarize the number of times a host triggered a signature. The interval between summaries is defined by the Signatures::summary_interval variable.

PacketFilter::Compile_Failure

(present if base/frameworks/packet-filter/main.bro is loaded)

This notice is generated if a packet filter cannot be compiled.

PacketFilter::Install_Failure

(present if base/frameworks/packet-filter/main.bro is loaded)

Generated if a packet filter fails to install.

PacketFilter::Too_Long_To_Compile_Filter

(present if base/frameworks/packet-filter/main.bro is loaded)

Generated when a notice takes too long to compile.

PacketFilter::Dropped_Packets

(present if base/frameworks/packet-filter/netstats.bro is loaded)

Indicates packets were dropped by the packet filter.

ProtocolDetector::Protocol_Found

(present if policy/frameworks/dpd/detect-protocols.bro is loaded)

ProtocolDetector::Server_Found

(present if policy/frameworks/dpd/detect-protocols.bro is loaded)

Intel::Notice

(present if policy/frameworks/intel/do_notice.bro is loaded)

This notice is generated when an intelligence indicator is denoted to be notice-worthy.

TeamCymruMalwareHashRegistry::Match

(present if policy/frameworks/files/detect-MHR.bro is loaded)

The hash value of a file transferred over HTTP matched in the malware hash registry.

PacketFilter::No_More_Conn_Shunts_Available

(present if policy/frameworks/packet-filter/shunt.bro is loaded)

Indicative that PacketFilter::max_bpf_shunts connections are already being shunted with BPF filters and no more are allowed.

PacketFilter::Cannot_BPF_Shunt_Conn

(present if policy/frameworks/packet-filter/shunt.bro is loaded)

Limitations in BPF make shunting some connections with BPF impossible. This notice encompasses those various cases.

Software::Software_Version_Change

(present if policy/frameworks/software/version-changes.bro is loaded)

For certain software, a version changing may matter. In that case, this notice will be generated. Software that matters if the version changes can be configured with the Software::interesting_version_changes variable.

Software::Vulnerable_Version

(present if policy/frameworks/software/vulnerable.bro is loaded)

Indicates that a vulnerable version of software was detected.

CaptureLoss::Too_Much_Loss

(present if policy/misc/capture-loss.bro is loaded)

Report if the detected capture loss exceeds the percentage threshold.

Traceroute::Detected

(present if policy/misc/detect-traceroute/main.bro is loaded)

Indicates that a host was seen running traceroutes. For more detail about specific traceroutes that we run, refer to the traceroute.log.

Scan::Address_Scan

(present if policy/misc/scan.bro is loaded)

Address scans detect that a host appears to be scanning some number of destinations on a single port. This notice is generated when more than Scan::addr_scan_threshold unique hosts are seen over the previous Scan::addr_scan_interval time range.

Scan::Port_Scan

(present if policy/misc/scan.bro is loaded)

Port scans detect that an attacking host appears to be scanning a single victim host on several ports. This notice is generated when an attacking host attempts to connect to Scan::port_scan_threshold unique ports on a single host over the previous Scan::port_scan_interval time range.

Conn::Retransmission_Inconsistency

(present if policy/protocols/conn/weirds.bro is loaded)

Possible evasion; usually just chud.

Conn::Content_Gap

(present if policy/protocols/conn/weirds.bro is loaded)

Data has sequence hole; perhaps due to filtering.

DNS::External_Name

(present if policy/protocols/dns/detect-external-names.bro is loaded)

Raised when a non-local name is found to be pointing at a local host. The Site::local_zones variable must be set appropriately for this detection.

FTP::Bruteforcing

(present if policy/protocols/ftp/detect-bruteforcing.bro is loaded)

Indicates a host bruteforcing FTP logins by watching for too many rejected usernames or failed passwords.

FTP::Site_Exec_Success

(present if policy/protocols/ftp/detect.bro is loaded)

Indicates that a successful response to a “SITE EXEC” command/arg pair was seen.

HTTP::SQL_Injection_Attacker

(present if policy/protocols/http/detect-sqli.bro is loaded)

Indicates that a host performing SQL injection attacks was detected.

HTTP::SQL_Injection_Victim

(present if policy/protocols/http/detect-sqli.bro is loaded)

Indicates that a host was seen to have SQL injection attacks against it. This is tracked by IP address as opposed to hostname.

SMTP::Blocklist_Error_Message

(present if policy/protocols/smtp/blocklists.bro is loaded)

An SMTP server sent a reply mentioning an SMTP block list.

SMTP::Blocklist_Blocked_Host

(present if policy/protocols/smtp/blocklists.bro is loaded)

The originator’s address is seen in the block list error message. This is useful to detect local hosts sending SPAM with a high positive rate.

SMTP::Suspicious_Origination

(present if policy/protocols/smtp/detect-suspicious-orig.bro is loaded)

SSH::Password_Guessing

(present if policy/protocols/ssh/detect-bruteforcing.bro is loaded)

Indicates that a host has been identified as crossing the SSH::password_guesses_limit threshold with failed logins.

SSH::Login_By_Password_Guesser

(present if policy/protocols/ssh/detect-bruteforcing.bro is loaded)

Indicates that a host previously identified as a “password guesser” has now had a successful login attempt. This is not currently implemented.

SSH::Watched_Country_Login

(present if policy/protocols/ssh/geo-data.bro is loaded)

If an SSH login is seen to or from a “watched” country based on the SSH::watched_countries variable then this notice will be generated.

SSH::Interesting_Hostname_Login

(present if policy/protocols/ssh/interesting-hostnames.bro is loaded)

Generated if a login originates or responds with a host where the reverse hostname lookup resolves to a name matched by the SSH::interesting_hostnames regular expression.

SSL::Certificate_Expired

(present if policy/protocols/ssl/expiring-certs.bro is loaded)

Indicates that a certificate’s NotValidAfter date has lapsed and the certificate is now invalid.

SSL::Certificate_Expires_Soon

(present if policy/protocols/ssl/expiring-certs.bro is loaded)

Indicates that a certificate is going to expire within SSL::notify_when_cert_expiring_in.

SSL::Certificate_Not_Valid_Yet

(present if policy/protocols/ssl/expiring-certs.bro is loaded)

Indicates that a certificate’s NotValidBefore date is future dated.

Heartbleed::SSL_Heartbeat_Attack

(present if policy/protocols/ssl/heartbleed.bro is loaded)

Indicates that a host performed a heartbleed attack or scan.

Heartbleed::SSL_Heartbeat_Attack_Success

(present if policy/protocols/ssl/heartbleed.bro is loaded)

Indicates that a host performing a heartbleed attack was probably successful.

Heartbleed::SSL_Heartbeat_Odd_Length

(present if policy/protocols/ssl/heartbleed.bro is loaded)

Indicates we saw heartbeat requests with odd length. Probably an attack or scan.

Heartbleed::SSL_Heartbeat_Many_Requests

(present if policy/protocols/ssl/heartbleed.bro is loaded)

Indicates we saw many heartbeat requests without a reply. Might be an attack.

SSL::Invalid_Server_Cert

(present if policy/protocols/ssl/validate-certs.bro is loaded)

This notice indicates that the result of validating the certificate along with its full certificate chain was invalid.

SSL::Invalid_Ocsp_Response

(present if policy/protocols/ssl/validate-ocsp.bro is loaded)

This indicates that the OCSP response was not deemed to be valid.

SSL::Weak_Key

(present if policy/protocols/ssl/weak-keys.bro is loaded)

Indicates that a server is using a potentially unsafe key.

SSL::Old_Version

(present if policy/protocols/ssl/weak-keys.bro is loaded)

Indicates that a server is using a potentially unsafe version

SSL::Weak_Cipher

(present if policy/protocols/ssl/weak-keys.bro is loaded)

Indicates that a server is using a potentially unsafe cipher

BroxygenExample::Broxygen_One

(present if broxygen/example.bro is loaded)

Any number of this type of comment will document “Broxygen_One”.

BroxygenExample::Broxygen_Two

(present if broxygen/example.bro is loaded)

Any number of this type of comment will document “BROXYGEN_TWO”.

BroxygenExample::Broxygen_Three

(present if broxygen/example.bro is loaded)

BroxygenExample::Broxygen_Four

(present if broxygen/example.bro is loaded)

Omitting comments is fine, and so is mixing ## and ##<, but it’s probably best to use only one style consistently.

Scripts creating new notices need to redef this enum to add their own specific notice types which would then get used when they call the NOTICE function. The convention is to give a general category along with the specific notice separating words with underscores and using leading capitals on each word except for abbreviations which are kept in all capitals. For example, SSH::Password_Guessing is for hosts that have crossed a threshold of failed SSH logins.

Events

Notice::begin_suppression

Type:event (ts: time, suppress_for: interval, note: Notice::Type, identifier: string)

This event is generated when a notice begins to be suppressed.

Ts:time indicating then when the notice to be suppressed occured. Suppress_for:length of time that this notice should be suppressed. Note:The Notice::Type of the notice. Identifier:The identifier string of the notice that should be suppressed.

Notice::cluster_notice

Type:event (n: Notice::Info)

This is the event used to transport notices on the cluster.

N:The notice information to be sent to the cluster manager for further processing.

Notice::log_notice

Type:event (rec: Notice::Info)

This event can be handled to access the Notice::Info record as it is sent on to the logging framework.

Rec:The record containing notice data before it is logged.

Notice::suppressed

Type:event (n: Notice::Info)

This event is generated on each occurrence of an event being suppressed.

N:The record containing notice data regarding the notice type being suppressed.

Hooks

Notice::notice

Type:hook (n: Notice::Info) : bool

This is the event that is called as the entry point to the notice framework by the global NOTICE function. By the time this event is generated, default values have already been filled out in the Notice::Info record and the notice policy has also been applied.

N:The record containing notice data.

Notice::policy

Type:hook (n: Notice::Info) : bool

The hook to modify notice handling.

Functions

NOTICE

Type:function (n: Notice::Info) : void

Notice::create_file_info

Type:function (f: fa_file) : Notice::FileInfo

Creates a record containing a subset of a full fa_file record.

F:record containing metadata about a file. Returns:record containing a subset of fields copied from f.

Notice::email_headers

Type:function (subject_desc: string, dest: string) : string

Constructs mail headers to which an email body can be appended for sending with sendmail.

Subject_desc:a subject string to use for the mail. Dest:recipient string to use for the mail. Returns:a string of mail headers to which an email body can be appended.

Notice::email_notice_to

Type:function (n: Notice::Info, dest: string, extend: bool) : void

Call this function to send a notice in an email. It is already used by default with the built in Notice::ACTION_EMAIL and Notice::ACTION_PAGE actions.

N:The record of notice data to email. Dest:The intended recipient of the notice email. Extend:Whether to extend the email using the email_body_sections field of n.

Notice::internal_NOTICE

Type:function (n: Notice::Info) : void

This is an internal wrapper for the global NOTICE function; disregard.

N:The record of notice data.

Notice::is_being_suppressed

Type:function (n: Notice::Info) : bool

A function to determine if an event is supposed to be suppressed.

N:The record containing the notice in question.

Notice::log_mailing_postprocessor

Type:function (info: Log::RotationInfo) : bool

A log postprocessing function that implements emailing the contents of a log upon rotation to any configured Notice::mail_dest. The rotated log is removed upon being sent.

Info:A record containing the rotated log file information. Returns:True.

Notice::populate_file_info

Type:function (f: fa_file, n: Notice::Info) : void

Populates file-related fields in a notice info record.

F:record containing metadata about a file. N:a notice record that needs file-related fields populated.

Notice::populate_file_info2

Type:function (fi: Notice::FileInfo, n: Notice::Info) : void

Populates file-related fields in a notice info record.

Fi:record containing metadata about a file. N:a notice record that needs file-related fields populated.