Be careful of downloading the popular FTP app FileZilla. Cybercrooks have put together a malicious version which acts like the real thing, but passes login information to a hacker-controlled server.

One way to distinguish the real from the fake is the size. The fake app is actually 6.8MB smaller than the genuine article. You will also find that it is packed with two extra DLL libraries that aren't in the genuine program.

Avast warns: "Beware of malformed FileZilla FTP client versions 3.7.3 and 3.5.3. We have noticed an increased presence of these malware versions of famous open source FTP clients." "The [bogus] installer is mostly hosted on hacked websites with fake content," it adds.