{
  "family": "redsip",
  "sample_count": 1,
  "category": "trojan",
  "description": "<h3>Executive Summary</h3>\nRedSip 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.\n\n<h3>Infection Vector and Technical Capabilities</h3>\nRedSip 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.\n\nOnce active, RedSip focuses exclusively on VoIP espionage:\n<ul>\n<li><strong>SIP Credential Harvesting:</strong> 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.</li>\n<li><strong>Network Sniffing (SIP Interception):</strong> 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.</li>\n<li><strong>Toll Fraud Facilitation:</strong> 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.</li>\n</ul>\n\n<h3>Threat Assessment</h3>\nA 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).\n\n<h3>Incident Response and Remediation</h3>\n<ul>\n<li><strong>Immediate Credential Revocation:</strong> 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.</li>\n<li><strong>Endpoint Isolation and Telemetry Analysis:</strong> Isolate the endpoint. Utilize EDR to analyze the execution path and identify if any packet-sniffing drivers (like WinPcap) were covertly installed.</li>\n<li><strong>VoIP Network Hardening:</strong> 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.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "Trojan.RedSip",
    "Spyware.SIP",
    "Backdoor.RedSip",
    "TollFraud.Win32"
  ],
  "enrichment_level": "insufficient_information",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1555.003",
    "T1040",
    "T1056.001"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-07-02T07:28:51Z",
  "type": "Trojan / VoIP Spyware",
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}