FBI Warns of ISIS-Inspired Cyber Attacks on 9/11 Anniversary

— -- The FBI is warning that an ISIS-inspired group of hackers is threatening to mark today’s anniversary of the Sept. 11, 2001, attacks with a new cyber-assault against U.S. government-related websites.

Twitter users claiming to be associated with the group, branding themselves with the "hashtag" moniker #AmericaUnderHacks, have already been posting online what they say is sensitive information about U.S. government personnel. But the information is available through basic Internet searches and is "recycled" from several years ago, sources told ABC News.

Nevertheless, the FBI wants companies doing business with the U.S. government to be able to defend their networks should hackers try to "commemorate the anniversary of the terrorist attacks" with more serious action, according to a "private industry notification" issued Thursday citing the recent threats.

“Will penetrate … governmental sites in September 11 to commemorate the destroyed skyscrapers,” threatened one recent tweet from the ISIS-inspired group of hackers, who call themselves the “Islamic Cyber Army.”

It’s unclear how credible such threats are, and in its notice Thursday, the FBI characterized the threats only as “possible.”

But in its notice, the FBI says the group (ICA) has successfully “hacked and defaced” certain governmental websites, and similar campaigns by “extremist cyber actors” have targeted networks associated with the U.S. government and banking industry.

“ICA would most likely seek to attack targets of opportunity based on technical vulnerabilities and a perceived connection to the United States or other Western countries,” the FBI says in its notice to private companies. “Web site defacements and/or any possible unauthorized releases … of personally identifiable information (PII) by ICA likely would be accompanied by messages expressing support for ISIL, and possibly language threatening additional cyber or physical terrorist attacks.”

The notice also predicts ICA “is likely to make claims of responsibility” for any successful hacking activity online by other groups.

The FBI describes ICA as an “ISI[S]-sympathetic hacking group,” comprised of members of like-minded hackers from the “Elite Islamic State Hackers” and others.

In its notice Thursday, the FBI suggests several “precautionary measures” companies can take “to mitigate a range of potential hacktivism threats by this group.”