Siplog

Overview

Trojan:Win32/Siplog is a specialized Information Stealer designed specifically to target and compromise Voice over IP (VoIP) communications. Its primary objective is to silently monitor network traffic or hook into VoIP client software to capture SIP (Session Initiation Protocol) credentials, call logs, and potentially intercept the audio streams of active phone calls (`T1056`).

Understanding Siplog (VoIP Stealers)
To an end-user, the infection is completely invisible; their VoIP softphone (like X-Lite, Zoiper, or Skype) continues to function normally. For a security operations center (SOC), Siplog represents a severe breach of confidentiality. Stolen SIP credentials allow attackers to commit 'toll fraud' (routing expensive international calls through the corporate PBX), while intercepted audio can lead to devastating corporate espionage.

Execution and Interception Mechanics
Siplog is typically deployed as a secondary payload by a more generic dropper. Once active, it utilizes two primary methods. First, it may act as a local packet sniffer (`T1040`), monitoring the network interface for unencrypted SIP traffic (port 5060) to extract plain-text usernames and passwords used during authentication. Second, against encrypted or modern VoIP clients, it may utilize process injection and API hooking (`T1056.001`) to capture credentials directly from the softphone's memory before they are encrypted, or even hook the Windows audio APIs (like `waveInAddBuffer`) to record the actual voice conversation to a hidden `.wav` file for later exfiltration.

Indicators of Compromise & Impact
The impact ranges from significant financial loss due to toll fraud to the catastrophic compromise of sensitive corporate communications. Host-based IoCs include EDR alerts for anomalous processes loading `wpcap.dll` (WinPcap) to facilitate packet sniffing, or suspicious DLL injection into known VoIP client executables. A critical IoC is the sudden appearance of large, hidden audio files (e.g., `.wav` or `.mp3`) in temporary directories. Network IoCs include the malware attempting to exfiltrate these large files to unknown external FTP or HTTP servers.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1056: Monitor for unauthorized keylogging, screen capturing, or web browser API hooking. Deploy EDR to detect API hooking.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_SIPLOG {
    meta:
        description = "Detects Siplog (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "siplog" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Siplog Activity
id: 0c25f91c6e0628648bd2303039bb428c
status: experimental
description: Detects generic indicators of the siplog malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*siplog*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Immediately isolate the compromised endpoint and revoke the SIP credentials associated with the user's softphone extension.
2. Review PBX or SIP trunk billing logs immediately for anomalous international calling patterns indicative of toll fraud.
3. Hunt for instances of unauthorized packet capture drivers (like WinPcap or Npcap) installed on standard user workstations.
4. Enforce TLS encryption for all SIP signaling (SIPS) and SRTP for audio media to mitigate local network sniffing.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not assume the compromise is limited to the endpoint; if SIP credentials were stolen, the corporate PBX is now under attack.
2. Avoid relying solely on basic AV to detect audio hooking; EDR behavioral analysis is required to catch API interception.

References & External Analysis

• Search "siplog" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Attack
• Retefe
• Quasar
• Snarasite
• Juicypotato

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/api/siplog.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.