Rootkit writers have started exploiting a loophole that lets them write malware able to bypass the PatchGuard driver signing protection built into 64-bit versions of Windows, Kaspersky Lab has reported. A product of the BlackHole Exploit Kit, a hugely successful kit for building malware to hit specific software vulnerabilities, the first element of the attack on a system is straightforward enough, using a downloader to hit the system through two common Java and Adobe Reader software flaws. On 64-bit Windows systems open to these exploits, this calls a 64-bit rootkit, Rootkit.Win64.Necurs.a., which executes the 'bcdedit.exe -set TESTSIGNING ON command, normally...