Check out the European Institute for Computer Anti-Virus Research (eicar) Anti-Virus Test File page. EICAR provides test files you can send to your users to determine if their anti-virus software is functioning correctly. We’ve seen this work fine on Trend Micro and Norton Anti-Virus software, but most ant-virus software should correctly detect these files. To generate this file yourself, just put the following string in a text file:
Note that the third character is a capital letter “O”, and that all letters must be on the first line of the file.