FortiSIEM Rules

Windows: Suspicious Non-Browser Network Communication With Google API

Rule ID


Default Status



Detects a non-browser process interacting with the Google API which could indicate the use of a covert C2 such as Google Sheet C2 (GC2-sheet). This rule is adapted from







Persistence consists of techniques that adversaries use to keep access to systems across restarts, changed credentials, and other interruptions that could cut off their access. Techniques used for persistence include any access, action, or configuration changes that let them maintain their foothold on systems, such as replacing or hijacking legitimate code or adding startup code.

MITRE ATT&CK® Techniques

No Technique Specified



Data Source

Windows Sysmon via FortiSIEM Agent



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.

300 seconds

Trigger Conditions

If the following defined pattern/s occur within a 300 second time window.


SubPattern Definitions

SubPattern Name: Filter

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 REGEXP "Win-Sysmon-3-Network-Connect.*" AND destName REGEXP ".*drive\.googleapis\.com.*|.*oauth2\.googleapis\.com.*|.*sheets\.googleapis\.com.*|.*www\.googleapis\.com.*" AND ((procName NOT REGEXP "\\brave\.exe$") AND (procName NOT IN ("C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe","C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe")) AND (procName NOT REGEXP "^C:\\Program Files\\Google\\Drive File Stream\*\\GoogleDriveFS\.exe|^C:\\Program Files\\Google\\Drive File Stream\\") AND (procName NOT IN ("C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe","C:\\Program Files\\Mozilla Firefox\\firefox.exe")) AND (procName NOT IN ("C:\\Program Files (x86)\\Internet Explorer\\iexplore.exe","C:\\Program Files\\Internet Explorer\\iexplore.exe")) AND (procName NOT REGEXP "\\maxthon\.exe$") AND (procName NOT REGEXP "^C:\\Program Files \(x86\)\\Microsoft\\EdgeWebView\\Application\\" AND procName NOT REGEXP "\\WindowsApps\\MicrosoftEdge\.exe$" AND procName NOT IN ("C:\\Program Files (x86)\\Microsoft\\Edge\\Application\\msedge.exe","C:\\Program Files\\Microsoft\\Edge\\Application\\msedge.exe")) AND (procName NOT REGEXP "^C:\\Program Files \(x86\)\\Microsoft\\EdgeCore\\|^C:\\Program Files\\Microsoft\\EdgeCore\\" OR procName NOT REGEXP "\\msedge\.exe$|\\msedgewebview2\.exe$") AND (procName NOT REGEXP "\\opera\.exe$") AND (procName NOT REGEXP "\\safari\.exe$") AND (procName NOT REGEXP "\\seamonkey\.exe$") AND (procName NOT REGEXP "\\vivaldi\.exe$") AND (procName NOT REGEXP "\\whale\.exe$") AND (procName NOT REGEXP "\\GoogleUpdate\.exe$") AND (procName NOT REGEXP "\\outlook\.exe$") AND (procName NOT REGEXP "\\teams\.exe$"))

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


Aggregate Constraint

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

COUNT(*) >= 1

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

destName = Filter.destName,
hostName = Filter.hostName,
procName = Filter.procName