Nerval's Lobster writes: On the same day the world discovered Western intelligence agencies were siphoning user information from Angry Birds and other popular smartphone apps, a leading antivirus developer revealed hackers are doing the same thing with one of the most popular open-source applications on the Internet. Maliciously modified versions of the popular file-transfer protocol (FTP) application FileZilla look and act just like the real thing, but include extra code that steals the login data typed in by users and sends it to an unauthorized server using the same FTP operation launched by the user without going through a firewall that might spot what it’s doing, according to an alert posted this afternoon by antivirus developer Avast Software. The malicious version is fully functional, uses the same graphical interface and component file names as the original, and masks itself further by avoiding any suspicious entries in the system registry, overt attempts to communicate with outside servers or other changes, according to the Jan. 27 alert from Avast. The most obvious differences are that the poisoned version of filezilla.exe is 6.8MB smaller than the real thing and there are two DLL libraries included in the fake that are not present in the original. They are labeled ibgcc_s_dw2-1.dll and libstdc++-6.dll, according to Avast. The official version’s Nullsoft installer is v2.45-Unicode; the evil twin uses v2.46.3-Unicode. Automatic updates also fail on the poisoned version “which is most likely a protection to prevent overwriting of the malware binaries,” Avast added.