Suspicious GUP Usage

About the rule

Rule Type

Standard

Rule Description

GUP.exe (Google Update Process or “Generic Updater”) is a legitimate updater tool included with applications such as Notepad++ and other third-party products, responsible for downloading and applying software updates. Attackers may abuse GUP.exe to execute arbitrary commands, download malicious payloads, or connect to external resources by launching it with crafted command-line arguments or through DLL hijacking. This rule detects anomalous or suspicious uses of GUP.exe, such as unexpected command-line parameters, connections to untrusted remote servers, or file operations outside standard update directories.

Severity

Trouble

Rule journey

Attack chain scenario

Initial access → Phishing or software supply chain compromise → Execution → Abuse of GUP.exe → Impact

Impact

• Defense evasion
• Unauthorized command execution
• Malware download or deployment
• Data exfiltration
• System persistence

Rule Requirement

Prerequisites

Use the Group Policy Management Console to audit process creation and process termination.

Install Sysmon from Microsoft Sysinternals and download the Sysmon configuration file that includes process creation monitoring. Add network connection events to the configuration file to monitor all network activity.

Create a new registry key "Microsoft-Windows-Sysmon/Operational" in the directory "Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\" if not already created.

Criteria

Detection

Execution Mode

realtime

Log Sources

Windows

MITRE ATT&CK

Defense Evasion: Hijack Execution Flow - DLL Side-Loading (T1574.002), Persistence: Hijack Execution Flow - DLL Side-Loading (T1574.002), Privilege Escalation: Hijack Execution Flow - DLL Side-Loading (T1574.002)

Security Standards

Enabling this rule will help you meet the security standard's requirement listed below:

DE.CM-01: Networks and network services are monitored to find potentially adverse events.

When this rule is triggered, you’re notified of suspicious usage of GUP.exe, such as non-standard command-line arguments, unauthorized network connections, or abnormal file operations. This enables you to review process activity, scrutinize update mechanisms, and promptly identify anomalous GUP.exe behavior, supporting effective monitoring and timely remediation of potential threats.

Author

Florian Roth (Nextron Systems)

Future actions

Known False Positives

This rule may be triggered during legitimate third-party software updates, especially if updates use custom arguments or internal repositories. Assess command-line parameters, update sources, and file paths for legitimacy before escalation.

Next Steps

When this rule is triggered, the following measures can be implemented:

1. Identification: Identify if the flagged event is a new incident or part of an existing incident.
2. Analysis: Analyze the impact and extent of the incident to comprehend the severity of the attack using the Incident Workbench.
3. Response: Respond promptly by initiating an automated workflow to interrupt the network connections and cease the malicious process.
4. Reconfiguration: Update allowlists for authorized internal GUP usage, enhance monitoring rules, and review detection analytics to prevent evasion or recurrence.

Mitigation