F-Secure Online Scanner

What we liked:
F-Secure's online scanner functions like traditional anti-virus and anti-spyware software and features a similar range of options. It downloads a small file that presents a simply designed window offering three types of scan: you can choose either a quick scan that looks at the locations most likely to harbour malware, a full scan that examines all drives and files on your system, or you can select which items you want to have checked. 

The impressive selection of scanning options lets you enable or disable spyware scanning, detect rootkits, examine all files or just programs and documents, and skip or look inside archives, such as Zip files. This is exactly what you want from an online scanner.

How it can be improved:
The definitions file is irritatingly large, requiring you to download a total of 72MB the first time you use it. The scanner works with Internet Explorer and Firefox but Safari and Chrome aren't supported, which makes ESET a faster and more versatile option.