Overview

Virus:Win32/Sivis is a destructive, polymorphic file infector that aggressively prepends its malicious code to executable files, causing widespread system corruption.

Understanding Sivis
To an end-user, Sivis causes applications to crash instantly upon opening and severely degrades system performance. For malware analysts, Sivis represents a classic, devastating viral threat. It is a parasitic virus; it does not just drop files onto the disk, it physically alters existing, legitimate executables (.exe files). Every time a user attempts to open an infected program, the virus executes first, spreading itself further before attempting to load the original application.

Execution and Evasion Strategies
Sivis typically infiltrates environments via infected USB drives, peer-to-peer file sharing, or as a secondary payload dropped by a trojan. Once active in memory, it scans the local hard drive and all mapped network shares for executable files. It utilizes polymorphism, altering its decryption loop and code structure with every infection, ensuring that no two infected files share the exact same cryptographic hash (MD5/SHA-256), thereby breaking traditional static AV signatures.

Indicators of Compromise & Impact
Incident responders should look for a sudden, massive wave of file modifications across the %ProgramFiles% directory. Anomalous spikes in CPU usage as the virus rapidly encrypts and prepends its code to files is a strong indicator. Due to its aggressive nature, Sivis often corrupts the PE (Portable Executable) headers of the files it infects, rendering them permanently unrecoverable. The impact is a total loss of application integrity across the host.

MITRE ATT&CK Techniques

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

Technique	Name	Tactic
`T1055`	Process Injection	Defense Evasion
`T1140`	Deobfuscate/Decode Files or Information	Defense Evasion
`T1485`	Data Destruction	Impact
`T1091`	Replication Through Removable Media	Lateral Movement
`T1106`	Native API	Execution

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_SIVIS {
    meta:
        description = "Detects Sivis (file_infector)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "sivis" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Sivis Activity
id: 962eb10ef9276d70f462e0bc163c6136
status: experimental
description: Detects generic indicators of the sivis malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*sivis*"
    condition: selection
level: medium

Containment & Response Steps

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

Instantly sever the endpoint from the network; Sivis will aggressively hunt for and infect executables on shared corporate network drives.
Assume all <code>.exe</code> and <code>.scr</code> files on the host are compromised and potentially corrupted beyond repair.
Do not attempt to 'clean' the files using standard AV, as this frequently destroys the legitimate application data appended to the virus.
Perform a complete bare-metal rebuild of the operating system and restore applications from known-clean, read-only installation media.

What to Avoid

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

Avoid backing up executable files from the infected machine; you will only be backing up the polymorphic viral payloads.
Do not execute any diagnostic tools directly from the infected host, as they will likely become infected upon execution.

Sivis

Overview

MITRE ATT&CK Techniques

Generated Detections (Boilerplate)

YARA Rule

Sigma Rule

Containment & Response Steps

What to Avoid

References & External Analysis

Related Families (Category: file_infector)

Machine-readable

Ecosystem & Interactive Environments