PH_Rule_Stat_14
Enabled
Detects a sudden increase in system memory usage - over a 30 minute interval, either the physical or virtual memory is 25% more than the statistical average over that same time period and the current physical memory usage is at least 50%
7
Performance
Impact
Impact consists of techniques that adversaries use to disrupt availability or compromise integrity by manipulating business and operational processes. Techniques used for impact can include destroying or tampering with data. In some cases, business processes can look fine, but may have been altered to benefit the adversaries’ goals. These techniques might be used by adversaries to follow through on their end goal or to provide cover for a confidentiality breach.
https://attack.mitre.org/tactics/TA0040T1499.001
Endpoint Denial of Service: OS Exhaustion Flood
Adversaries may target the operating system (OS) for a DoS attack, since the (OS) is responsible for managing the finite resources on a system. These attacks do not need to exhaust the actual resources on a system since they can simply exhaust the limits that an OS self-imposes to prevent the entire system from being overwhelmed by excessive demands on its capacity.
https://attack.mitre.org/techniques/T1499/001Network
FortiSIEM Profiling
Profiling
Identify the process that is consuming high memory and determine the root cause.
If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.
1800 seconds
If the following defined pattern/s occur within a 1800 second time window.
StatResource
This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.
This is the query logic that matches incoming events
eventType IN ("PH_DEV_MON_SYS_MEM_UTIL","PH_DEV_MON_FORTIGATE_PERF","PH_DEV_MON_FORTISWITCH_PERF","PH_DEV_MON_FORTIAP_PERF")
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
hostName,hostIpAddr
This is most typically a numerical constraint that defines when the rule should trigger an incident
((AVG(memUtil) >= 1.25 * STAT_AVG(AVG(memUtil):109) AND AVG(memUtil) >= 50) OR
(AVG(virtMemUtil) >= 1.25 * STAT_AVG(AVG(virtMemUtil):109) AND AVG(virtMemUtil) >= 65)) AND COUNT(*) >= 3
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
hostName = StatResource.hostName,
hostIpAddr = StatResource.hostIpAddr,
memUtil = StatResource.AVG(memUtil),
virtMemUtil = StatResource.AVG(virtMemUtil),
avgMemUtil = StatResource.STAT_AVG(AVG(memUtil):109),
avgVirtMemUtil = StatResource.STAT_AVG(AVG(virtMemUtil):109)