to complete an anti-virus or anti-malware scan depends
on a variety of factors
- The program itself and how its scanning engine is designed to scan: using a signature database vs heuristic scanning for suspicious behavior or a combination of both.
- Options to scan for spyware, adware, riskware and potentially unwanted or unsafe programs (PUPs).
- Options to scan memory, boot sectors, registry and alternate data streams (ADS).
- Type of scan performed: Deep, Quick or Custom scanning.
- What action has to be performed when malware is detected.
- A computer's hard drive size.
- Disk used capacity (number of files to include temporary files) that have to be scanned.
- Types of files (.exe, .dll, .sys, .cab, archived, compressed, packed, email, etc) that are scanned.
- Whether external drives are included in the scan.
- Competition for and utilization of system resources by the scanner.
- Other running processes and programs in the background.
- Interference from malware.
- Interference from the user.
To speed up your scans, uninstall unnecessary programs, clean out the temporary files
or use ATF Cleaner
first, temporarily disable any other real-time protection tools
, close all open programs and do not use
the computer during the scan. If the scan still seems slow or hangs, then try performing the scan in "safe mode
".Note: It is not unusual for an anti-virus or anti-malware scanner to be suspicious of some compressed, archived, .cab and packed files because they have difficulty reading what is inside them. These kind of files often trigger alerts by security software using heuristic detection because they are resistant to scanning (difficult to read). This resistance may also result in some scanners to stall (hang) on these particular types of files. Certain files in the System Volume Information Folder like the Tracking.log (created by the Distributed Link Tracking Service to store maintenance information) have also been reported as a source causing some scanners to hang.
For a more detailed explanation, see How an Antivirus Program Works