Windows: Potential Dead Drop Resolvers

Rule ID

PH_Rule_SIGMA_2049

Default Status

Enabled

Description

Detects an executable, which is not an internet browser, making DNS request to legit popular websites, which were seen to be used as dead drop resolvers in previous attacks. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/network_connection/net_connection_win_dead_drop_resolvers.yml

Severity

MITRE ATT&CK® Tactics

Command And Control

MITRE ATT&CK® Techniques

T1102.001

Web Service: Dead Drop Resolver

Adversaries may use an existing, legitimate external Web service to host information that points to additional command and control (C2) infrastructure. Adversaries may post content, known as a dead drop resolver, on Web services with embedded (and often obfuscated/encoded) domains or IP addresses. Once infected, victims will reach out to and be redirected by these resolvers. Use of a dead drop resolver may also protect back-end C2 infrastructure from discovery through malware binary analysis while also enabling operational resiliency (since this infrastructure may be dynamically changed).

https://attack.mitre.org/techniques/T1102/001

Impacts

Server

Data Source

Windows Sysmon via FortiSIEM Agent

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.

300 seconds

Trigger Conditions

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

Filter

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 ((initiated="true" AND destName REGEXP "\.cloudflare\.com$|\.githubusercontent\.com$|cdn\.discordapp\.com$|docs\.google\.com$|facebook\.com$|feeds\.rapidfeeds\.com$|fotolog\.com$|imgur\.com$|livejournal\.com$|paste\.ee$|pastebin\.com$|pastebin\.pl$|pastetext\.net$|reddit\.com$|steamcommunity\.com$|technet\.microsoft\.com$|twitter\.com$|youtube\.com$") AND ((procName NOT REGEXP "\\brave\.exe$") AND (procName NOT IN ("C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe","C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe")) AND (procName NOT IN ("C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe","C:\\Program Files\\Mozilla Firefox\\firefox.exe")) AND (procName NOT IN ("C:\\Program Files (x86)\\Internet Explorer\\iexplore.exe","C:\\Program Files\\Internet Explorer\\iexplore.exe")) AND (procName NOT REGEXP "\\maxthon\.exe$") 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$"))) AND ((procName NOT REGEXP "\\MsMpEng\.exe$|\\MsSense\.exe$") AND (procName NOT REGEXP "\\PRTG Probe\.exe$") AND (procName NOT REGEXP "\\Engine\.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

destName,hostName,initiated,procName

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,
initiated = Filter.initiated,
procName = Filter.procName

FortiSIEM Rules