The Mac-specific Flashback Trojan created a zombie army of 550,000 Mac machines by exploiting a Java hole that Apple only patched on Tuesday, six weeks after Microsoft plugged it up on Windows machines.
This is according to Russian anti-virus firm Dr Web, which arrived at the figure after it successfully managed to sinkhole one of the command-and-control servers used to control Mac machines hit by the latest attack. The legions of compromised zombies were mostly located in the US (56.6 per cent, or 303,449 infected hosts), Canada (19.8 per cent, or 106,379 infected computers) and the UK (12.8 per cent or 68,577 cases of infection).
The Flashback malware was capable of installing itself on unprotected Mac machines without user interaction, a factor that goes a long way in explaining the success of its spread. Users become infected simply by visiting a site loaded with exploit code, in drive-by-download-style attacks.
The malware establishes a back door on compromised systems for the subsequent download of additional cyber-bugs.
Additional payloads downloaded by the malware included a data-stealing Trojan that attempts to lift passwords and banking information from Safari as well as a search-hijacking tool.
The later utility was probably designed to power click-fraud scams or to redirect victims towards scareware portals, net security firm Sophos notes.
Attackers first began to exploit two earlier Java vulnerabilities (CVE-2011-3544 and CVE-2008-5353) to spread malware in February 2012, before switching to another exploit (CVE-2012-0507) on 16 March – to devastating effect. ®