The Anti-Malware Scan Interface (AMSI) is a security technology developed by Microsoft that enables deeper, real-time inspection of scripts and code at run-time to detect and block malicious activity—especially malware that tries to evade traditional file-based scanning. AMSI provides an open interface that allows applications and services (like Microsoft SharePoint) to communicate with installed anti-malware solutions for scanning and analysis.

How AMSI Works

  • When a script (PowerShell, VBScript, JavaScript, etc.) or code executes, AMSI can intercept the contents—even if obfuscated or loaded in memory—and submit them to an installed anti-malware engine (such as Microsoft Defender Antivirus).
  • The anti-malware engine analyzes the code for suspicious or known malicious patterns before execution continues. If a threat is detected, it can block or quarantine the activity.

Benefits of AMSI

  • Detects In-Memory Attacks: AMSI can catch advanced threats that never touch disk, including fileless malware and scripts loaded from benign-seeming applications.
  • Vendor-Agnostic: Any security solution that implements the AMSI API can perform the scanning—not just Microsoft Defender.
  • Enhanced Protection: Integrating AMSI in applications like SharePoint fortifies defenses against exploits, backdoors, or credential theft, as attackers often use sophisticated in-memory techniques.
Synonyms:
Anti Malware Scan Interface, AMSI