Multi-engine anti-virus scanners are a great help when dealing with suspicious files as you are able to leverage the malware detection capabilities of multiple antivirus engines with most up-to-date definitions from a single interface. VirusTotal has been one of the most well-known such free service offering scanning of suspicious files and URLs with 42 anti-virus engines helping users reveal viruses, worms, trojans and other kinds of malicious content.

One of the most needed feature to make efficient use of multi-av scanning services is an browser helper utility which would enable users to scan URL's and files right from their web-browsers before visiting the suspicious link, thankfully VirusTotal team has realized this and a Firefox web-browser addon VTZilla is now available enabling users to right-click any suspicious link and launch a VirusTotal URL Scan and even pre-scan a file before downloading from the default "Firefox Download Save" dialog-box.