Excessive End User Mail

Rule ID

PH_Rule_Flow_19

Default Status

Enabled

Description

Detects a scenario where a host, that is itself not an authorized mail gateway, is sending excessive emails (more than 20 emails in 2 minutes). This behavior may indicate malware running on an end host that is trying to send spam or privileged information to its own set of mail servers (which may be compromised).

Severity

MITRE ATT&CK® Tactics

Collection

Collection consists of techniques adversaries may use to gather information and the sources information is collected from that are relevant to following through on the adversary's objectives. Frequently, the next goal after collecting data is to steal (exfiltrate) the data. Common target sources include various drive types, browsers, audio, video, and email. Common collection methods include capturing screenshots and keyboard input.

https://attack.mitre.org/tactics/TA0009

MITRE ATT&CK® Techniques

T1114.001

Email Collection: Local Email Collection

Adversaries may sniff network traffic to capture information about an environment, including authentication material passed over the network. Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. An adversary may place a network interface into promiscuous mode to passively access data in transit over the network, or use span ports to capture a larger amount of data.

https://attack.mitre.org/techniques/T1114/001

Impacts

Application

Data Source

FortiGate via Syslog or Netflow, Checkpoint via Syslog or Netflow, Palo Alto via Syslog or Netflow

Detection

Correlation

Remediation Guidance

No remediation guidance specified

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

120 seconds

Trigger Conditions

If the following defined pattern/s occur within a 120 second time window.

EndUserExcessMail

SubPattern Definitions

SubPattern Name: EndUserExcessMail

This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.

SubPattern Query

This is the query logic that matches incoming events

ipProto = 6 AND destIpPort = 25 AND srcIpAddr NOT IN (Group@PH_SYS_DEVICE_SEC_GW,Group@PH_SYS_APP_MAIL_SERVER) AND srcIpAddr IN (Group@PH_SYS_NETWORK_ENTERPRISE_INTERNAL_NET) AND eventType IN (Group@PH_SYS_EVENT_PermitNetTraffic, Group@PH_SYS_EVENT_NetflowTraffic, Group@PH_SYS_EVENT_BiNetflowTraffic,Group@PH_SYS_EVENT_DenyNetTraffic)

Group by Attributes

This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID

srcIpAddr

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 20

Incident Attribute Mapping

This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.

The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern

 srcIpAddr = EndUserExcessMail.srcIpAddr,
incidentCount = EndUserExcessMail.COUNT(*)

FortiSIEM Rules