FortiSIEM Rules

Outbreak: HAFNIUM Exchange OWA Server Authentication Bypass

Rule ID


Default Status



Detects HAFNIUM Suspicious OWA access in an attempt to bypass authntication via POST to certain directories in Exchange OWA Server. This needs Windows agents to be run on these server to get IIS logs.






Command and Control

Command and Control consists of techniques that adversaries may use to communicate with systems under their control within a victim network. Adversaries commonly attempt to mimic normal, expected traffic to avoid detection. There are many ways an adversary can establish command and control with various levels of stealth depending on the victim’s network structure and defenses.

MITRE ATT&CK® Techniques

No Technique Specified



Data Source

Microsoft IIS via FortiSIEM Agent



Remediation Guidance

Check if the source is patched for the CVE associated with the event. If yes then remove the host from the network and patch immediately. If host is not scanned then determine if the host is running the affected version of the application. If yes then patch immediately, else it is likely a false positive.

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: Hafnium

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 CONTAIN "AO-WUA-IIS-Web" AND httpMethod="POST" AND ( uriStem CONTAIN "/owa/auth/Current/themes/resources/" OR (uriStem CONTAIN "/owa/auth/Current/" AND httpUserAgent IN ("DuckDuckBot/1.0;+(+","Mozilla/5.0+(X11;+Linux+x86_64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/51.0.2704.103+Safari/537.36","Mozilla/5.0+(compatible;+Baiduspider/2.0;++","Mozilla/5.0+(compatible;+Bingbot/2.0;++","Mozilla/5.0+(compatible;+Googlebot/2.1;++","Mozilla/5.0+(compatible;+Konqueror/3.5;+Linux)+KHTML/3.5.5+(like+Gecko)+(Exabot-Thumbnails)","Mozilla/5.0+(compatible;+Yahoo!+Slurp;+","Mozilla/5.0+(compatible;+YandexBot/3.0;++","facebookexternalhit/1.1+(+")) OR (uriStem CONTAIN "/ecp/" AND httpUserAgent IN ("ExchangeServicesClient/","python-requests/2.19.1","python-requests/2.25.1")) OR (uriStem REGEXP ".*/aspnet_client/.*|.*/owa/.*" AND httpUserAgent IN ("Googlebot/2.1+(+","Mozilla/5.0+(compatible;+Baiduspider/2.0;++","antSword/v2.1")) OR uriStem REGEXP ".*/ecp/default\.flt.*|.*/ecp/main\.css.*|.*/owa/auth/Current/.*" OR (uriStem REGEXP ".*/ecp/.*" AND uriStem REGEXP ".*\.js.*"))

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

 hostName = Hafnium.hostName