Antivirus Signature Differences Explained

TL;DR

Yes, virus signatures are different between antivirus programs. Each company uses its own methods for identifying threats and maintains a unique signature database. This means one antivirus might detect something another misses. Using multiple antiviruses (layered security) can improve protection.

Understanding Virus Signatures

Think of virus signatures as fingerprints for malicious software. When an antivirus scans your computer, it looks for these ‘fingerprints’ in files and programs. If a match is found, the file is flagged as potentially harmful.

Why Are Signatures Different?

1. Different Research Teams: Each cyber security company has its own team of analysts constantly discovering new malware. They analyse samples differently and prioritise threats based on their own intelligence.
2. Signature Creation Methods: The way signatures are created varies. Some focus on specific code patterns, others use behavioural analysis (how the program acts), or heuristics (general rules).
3. Database Size & Frequency of Updates: Signature databases aren’t static. They’re updated constantly. The speed and frequency of these updates differ between vendors. A faster update rate means quicker protection against new threats.
4. Proprietary Technology: Antivirus companies invest heavily in their technology, keeping signature creation algorithms secret to maintain a competitive edge.

How Signatures Work (Simplified)

Signatures aren’t always full files. They can be:

• Hash Values: A unique code generated from the entire file. If even one character changes in the file, the hash value will change.
• Code Snippets: Specific sections of malicious code that are common across many variants of a virus.
• YARA Rules: More complex rules that look for patterns and characteristics within files (often used to identify families of malware). Example YARA rule:

  n

  rule example_malware {
     meta:
        description = "Detects a simple piece of malware"
        author = "Your Name"
     strings:
        $string1 = "suspicious string" nocase
        $string2 = "another suspicious string" nocase
     condition:
        all of ($string1, $string2)
  }
  

Testing Signature Differences

You can test this yourself (carefully!). Use a safe malware testing service like VirusTotal:

1. Go to: VirusTotal
2. Upload a Sample File: Only use files from reputable test sources! Never upload personal or sensitive data.
3. View the Results: VirusTotal scans the file with over 70 different antivirus engines and shows you which ones detect it, and which don’t. This clearly demonstrates signature differences.

What Does This Mean for You?

1. No Single Antivirus is Perfect: Relying on just one solution leaves you vulnerable.
2. Layered Security is Best: Combine different antivirus programs, a firewall, and good online habits (avoid suspicious links/downloads).
3. Regular Updates are Crucial: Ensure your antivirus software is always up-to-date to benefit from the latest signature definitions. You can usually check this within the program’s settings. For example, in Windows Security:

   Get-MpComputerStatus | Select-Object AMServiceEnabled, SignatureDatabaseVersion

4. Consider Behavioural Analysis: Look for antivirus solutions that go beyond signatures and use behavioural analysis to detect unknown threats.