Virtual Machine CPU Warning

Rule ID

PH_Rule_Perf_219

Default Status

Enabled

Description

Detects that virtual server CPU ready percent has reached a warning level (between 20% and 25% based on 2 successive readings in a 10 minute interval

Severity

MITRE ATT&CK® Tactics

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/TA0040

MITRE ATT&CK® Techniques

T1499.001

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/T1499/001

Impacts

Virtualization

Data Source

VCenter or ESX via VM_SDK

Detection

Correlation

Remediation Guidance

VM CPU Ready is a measure of the time a VM has to wait for CPU resources from the ESX host. VMware recommends CPU ready should be less than 5%. If the ready time values are high on the VM that experience bad performance, then check for CPU limiting: Make sure the VM is not constrained by a CPU limit set by itself. Make sure that the VM is not constrained by its resource pool. If there is no CPU limiting, then the host could be too oversubscribed.

Time Window

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

600 seconds

Trigger Conditions

If the following defined pattern/s occur within a 600 second time window.

VMCPUMedium

SubPattern Definitions

SubPattern Name: VMCPUMedium

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

eventType = "PH_DEV_MON_VM_CPU_UTIL"

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

hostName,hostIpAddr,phyMachIpAddr,phyMachName,vmName,relayDevIpAddr

Aggregate Constraint

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

AVG(cpuReadyPct) >= DeviceToCMDBAttr(hostIpAddr,ReadyCPUPctThreshWarn) AND AVG(cpuReadyPct) < DeviceToCMDBAttr(hostIpAddr,ReadyCPUPctThreshCrit)  AND COUNT(*) >= 2

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

 hostIpAddr = VMCPUMedium.hostIpAddr,
hostName = VMCPUMedium.hostName,
phyMachIpAddr = VMCPUMedium.phyMachIpAddr,
phyMachName = VMCPUMedium.phyMachName,
cpuReadyPct = VMCPUMedium.AVG(cpuReadyPct),
vmName = VMCPUMedium.vmName,
relayDevIpAddr = VMCPUMedium.relayDevIpAddr

FortiSIEM Rules