Activist hackers linked to the collective known as Anonymous have secretly accessed US government computers in multiple agencies and stolen sensitive information in a campaign that began almost a year ago, the FBI has warned.
The hackers exploited a flaw in the software of Adobe Systems to launch a rash of electronic break-ins that began last December, then left "back doors" to return to many of the machines as recently as last month, the Federal Bureau of Investigation said in a memo.
It described the attacks as "a widespread problem that should be addressed", adding that the breach affected the US Army, Department of Energy, Department of Health and Human Services, and perhaps many more agencies.
Investigators are still gathering information on the scope of the cybercampaign, which the authorities believe is continuing.
The FBI document tells system administrators what to look for to determine if their systems are compromised. According to an internal e-mail from Energy Secretary Ernest Moniz' chief of staff, Kevin Knobloch, the stolen data included personal information on at least 104,000 employees, contractors, family members and others associated with the Department of Energy, along with information on almost 20,000 bank accounts.
The email, dated October 11, said officials were "very concerned" that loss of the banking information could lead to theft attempts.
Officials said the hacking was linked to the case of Lauri Love, a British resident indicted on October 28 for allegedly hacking into computers at the US Department of Energy, the army, the Department of Health and Human Services and elsewhere.
Investigators believe the attacks began when Love and others took advantage of a security flaw in Adobe's ColdFusion software, used to build websites.
Adobe spokeswoman Heather Edell said the majority of attacks involving the firm's software had exploited programs that were not updated with the latest security patches.