Event Based Rules Syntax

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Threat Stack collects raw event data from the agents installed on your machines and delivers it to our application for processing. Then we use the Base Rule Set and any rules that you created to fire alerts based on information you want to get detail on.

This article explains the types of event rules and the syntax associated with the events. This information will enable you to search for events more efficiently and make better suppressions and rule filters to refine the information you see inside of Threat Stack.

Rule Categories

Threat Stack provides the following rule categories based on the following event types.

Types	Event type rules process....
Audit	Syscall events from the audit framework
CloudTrail	AWS CloudTrail events
File	Local file system events for file integrity monitoring
Host	Events triggered from host logs
Login	Local login events
Threat Intel	IP reputation events

Search Syntax Best Practices

This section includes best practices that apply to searching across all event types:

1. The search field is case sensitive, all event types must be lowercase.
2. You can use parentheses when searching multiples of the same:
• parameters
• key value pairs
3. The Alert Details section enables a Add to Search option, this add key values to your search with the correct syntax.
4. The server syntax for “agent” is consistent across all event types for rules, this searches for the "hostname".

Note

Threat Stack uses the CloudTrail native case for compatibility reasons. This means the test filter is case sensitive and uppercase letters will cause the test filter not to match even if a suppression or rule filter is actually correct.

Audit Event Syntax

Audit event syntax contains a readable, parseable version of linux syscalls. This provides a comprehensive look into all local actions taken by your operating system.

To search an audit event, enter `event_type = “audit”` into the search field. You can use AND or OR operators to add key values to your search.

Notable key values pairs for audit events include:

Title (Type)	Key Value Pairs
Made Connection (type = “connect”)	src_addr, src_port, dst_port, ip, port, service, exe, user, group, PID, PPID, command, session
Accepted connection (type = “accept”)	src_addr, src_port, ip, port, exe, user, group, PID, PPID, command, session
Start (type = “start”)	exe, cwd, user, group, PID, PPID command, session, arguments
Bind Name to Socket (type = “bind”)	ip, port, exe, user, group, PID, PPID, command, session
Listen for socket connections (type = “listen”)	exe, user, group, PID, PPID, command, session
Load a kernel module (type = “finit_module”)	exe, user, group, PID, PPID, command, session
Get & set socket options (type = “setsockopt”)	exe, user, group, PID, PPID, command, session, tty

IP and Port fields are derived fields and are different for “connect” and “accept” events.

Title (Type)	Key Value Pairs	Threat Stack Use	Notes
Connect	IP and dst_port	The IP field is the destination ip of the connection. The port is the destination port (dst_port).
Accept	IP and dst_port	The IP field is the source IP of the remote connection. The port is the ephemeral (negotiated) return port for the tcp connection.	Network events are TCP connections only and do not include UDP connections.

CloudTrail Event Syntax

To search for a CloudTrail event, enter event_type = “cloudtrail” into the search field.

Due to the large number of CloudTrail events and key value pairs available and generated, Threat Stack does not index them all. This means, you cannot search every potential value pair. In rare cases, this means there could be information that you want to search, filter, or suppress that you would need to contact us to implement.

Warning

CloudTrail is case sensitivity for key value pairs, examples include “eventSource”, “eventName”, “user”, and “arnRole”.

Using operators such as “like”, “ends_with”, or “starts_with”, automatically make queries lowercase within Threat Stack which causes the search to fail. This only pertains to event searches not to rule cloning and creation, rule filters, or suppressions.

Notable CloudTrail Keys

server

region

requestID

eventID

arnRole

accountId

timestamp

event_type

ip

eventName

eventSource

eventSourceType

Note

AWS does not provide a CloudTrail validation API endpoint. This means that Threat Stack cannot distinguish between key value pairs that are not indexed or invalid key value pairs.

File Event Syntax

To search for a file integrity monitoring event, enter event_type = ”file” into the search field.

Common search would be by filename, command, argument, or user.

Title (type)	Key Value Pairs
File (event_type = “file”)	filename, command, arguments, or user

Host Event Syntax

To search for host events, enter event_type = ”host” into the search field.

• Login sessions: open and close
• Privilege escalations: successful and failed
• Failed login sessions

Key Value Pairs

users

group

src_ip

Search by users, group (have to know exactly what you are looking for syntax wise “authentication-success” or “authentication_failed” or “invalid_login” otherwise the search will fail), or source IP (src_ip).

Note

Threat Stack differentiates between “privilege escalation failed” and a “failed login session”.

You can also search for the “sigid”, it can differentiate within privilege escalation.

Login Event Syntax

To search for login events, enter event_type = ”login” into the search field.

Common searches for login events include “src_ip” or “server” “src_host”. Logout events are covered as Host events.

Key Value Pairs

src_host

agent

src_ip

Key value pair, key is the field and the value is the dynamic so for “src_ip” the value is the notated address. If you search “agent” you are searching "hostname”.

Threat Intel Event Syntax

Threat Intel refers to Threat Intelligence, you can search for Threat Intel events using event_type = “threatintel” in the search field.

Three important key value pairs: “threatintel_source”, ‘threatintel_reason”, and “ip” - people want to know what list it came from (source), what is the reputation (reason), and the location it came from (ip).

Key Value Pairs

user, command, arguments, port

threatintel_source, threatintel_reason, ip