Redsip
Overview
Executive Summary
RedSip is a highly specialized Trojan and backdoor designed specifically to target, intercept, and exploit Voice over IP (VoIP) communications, specifically focusing on the SIP (Session Initiation Protocol). Rather than stealing standard files, RedSip operates as an espionage tool, aiming to monitor telephone communications, steal SIP credentials, and potentially facilitate toll fraud by routing unauthorized calls through the compromised corporate PBX infrastructure.Infection Vector and Technical Capabilities
RedSip typically infects softphone clients (software-based VoIP phones) running on Windows endpoints. The initial vector is often a targeted phishing attack or the deployment of a secondary payload by an initial access broker. Once active, RedSip focuses exclusively on VoIP espionage:- SIP Credential Harvesting: The malware searches the infected endpoint for configuration files and registry entries associated with popular softphone applications (like X-Lite, MicroSIP, or Zoiper). It extracts the SIP server addresses, usernames, and plain-text (or weakly hashed) passwords used to authenticate to the corporate PBX.
- Network Sniffing (SIP Interception): Advanced variants of RedSip utilize network packet capture techniques (e.g., installing WinPcap or similar drivers) to sniff the local network interface for unencrypted SIP traffic (UDP port 5060). This allows the attacker to passively monitor call metadata (who is calling whom) and intercept authentication hashes.
- Toll Fraud Facilitation: By exfiltrating the SIP credentials to the C2 server, the threat actors can provision their own unauthorized softphones. They utilize the victim's PBX to make massive volumes of expensive, international premium-rate calls, leaving the victim organization with a devastating telecommunications bill.
Threat Assessment
A RedSip infection is a critical security and financial incident. It represents a severe breach of corporate communications privacy and poses a direct, immediate financial threat through the facilitation of toll fraud (PBX hacking).Incident Response and Remediation
- Immediate Credential Revocation: The highest priority is to immediately revoke and reset the SIP passwords for all extensions associated with the compromised endpoint at the PBX/VoIP server level to halt any ongoing toll fraud.
- Endpoint Isolation and Telemetry Analysis: Isolate the endpoint. Utilize EDR to analyze the execution path and identify if any packet-sniffing drivers (like WinPcap) were covertly installed.
- VoIP Network Hardening: IT administration must ensure that all internal VoIP communications are encrypted (using SIPS and SRTP) to prevent local network sniffing, and implement strict Geo-IP blocking and rate-limiting on the PBX to prevent international toll fraud.
Known aliases
Threat reports may refer to this family under multiple names:
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1555.003 T1040 T1056.001
Tactical Mitigations
Based on the techniques used by this family, consider the following defensive strategies:
- T1056.001: Implement Endpoint Detection and Response (EDR) to monitor for suspicious API calls related to keystroke interception. Enforce Multi-Factor Authentication (MFA) to render stolen passwords useless.
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_REDSIP {
meta:
description = "Detects Redsip (trojan)"
author = "SystemHelpdesk Boilerplate Generator"
date = "2026-07-06"
strings:
$s1 = "redsip" ascii wide nocase
$s2 = "trojan.redsip" ascii wide nocase
$s3 = "spyware.sip" ascii wide nocase
$s4 = "backdoor.redsip" ascii wide nocase
$s5 = "tollfraud.win32" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Sigma Rule
title: Suspicious Redsip Activity
id: f656e0bd8c91120d891ae5f4f214eda0
status: experimental
description: Detects generic indicators of the redsip malware family.
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith:
- '\cmd.exe'
- '\powershell.exe'
CommandLine|contains:
- "*redsip*"
- "*trojan.redsip*"
- "*spyware.sip*"
- "*backdoor.redsip*"
- "*tollfraud.win32*"
condition: selection
level: mediumReferences & External Analysis
- Search "redsip" on VirusTotal (External Analysis)
Frequently Asked Questions
How do I remove the Redsip Trojan from Windows?
Manual removal of Redsip is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
Is Redsip a virus or a Trojan?
Redsip is classified as a Trojan. Unlike traditional viruses that infect files, modern malware like Redsip typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Redsip infection?
Symptoms of Redsip can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Related Families (Category: trojan)
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Protect Your Network Against Trojans
Want to prevent Redsip and similar threats from compromising your organization? Read our comprehensive defensive guide: Banking Trojan Protection.
Machine-readable
Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/api/redsip.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.