The former director of the National Security Agency and the CIA speculated on Tuesday that hackers and transparency groups were likely to respond with cyber-terror attacks if the United States government apprehends whistleblower Edward Snowden.

"If and when our government grabs Edward Snowden, and brings him back here to the United States for trial, what does this group do?" said retired air force general Michael Hayden, who from 1999 to 2009 ran the NSA and then the CIA, referring to "nihilists, anarchists, activists, Lulzsec, Anonymous, twentysomethings who haven't talked to the opposite sex in five or six years".

"They may want to come after the US government, but frankly, you know, the dot-mil stuff is about the hardest target in the United States," Hayden said, using a shorthand for US military networks. "So if they can't create great harm to dot-mil, who are they going after? Who for them are the World Trade Centers? The World Trade Centers, as they were for al-Qaida."

Hayden provided his speculation during a speech on cybersecurity to a Washington group, the Bipartisan Policy Center, in which he confessed to being deliberately provocative.

Under Hayden, the NSA began to collect, among other things, the phone records and internet data of Americans without warrants after 9/11, a drastic departure from its traditional mission of collecting foreign intelligence. A variety of technically sophisticated collection and analysis programs, codenamed Stellar Wind, were the genesis of several of the NSA efforts that Snowden disclosed to the Guardian and the Washington Post.

Hayden said that the loose coalition of hacker groups and activists were "less capable" of inflicting actual harm on either US networks or physical infrastructure, but they grow technologically more sophisticated. Echoing years of rhetoric that has described terrorists, Hayden added that their "demands may be unsatisfiable".

Snowden recently received temporary asylum from Russia, allowing the former NSA contractor to leave the Sheremetyevo airport on Thursday, an act of defiance by Moscow toward the Obama administration.

Asked what he expected a potential cyber-terrorist attack related to Snowden to look like, Hayden clarified that he was being "entirely speculative, not predictive".

"I'm just trying to illustrate that you've got a group of people out there who make demands, whose demands may not be satisfiable, may not be rational, from other points of view, may not be the kinds of things that government can accommodate," Hayden said.

"But certainly Mr Snowden has created quite a stir among those folks who are very committed to transparency and global transparency and the global web, kind of ungoverned and free. And I don't know that there's a logic between trying to [punish] America or American institutions for his arrest, but I hold out the possibility. I can sit here and imagine circumstances and scenarios, but they're nothing more than imaginative."