WASHINGTON: US experts scored a cyberwarfare coup by targeting websites run by al Qaeda's Yemeni branch and changing the message to undermine their propaganda, according to US officials.

In a speech late Wednesday, Secretary of State Hillary Clinton attributed the success to the State Department's new Center for Strategic Communications, which also draws experts from the intelligence and defense communities.

One team, she said, targeted a propaganda campaign launched two weeks ago by the Yemeni-based al Qaeda in the Arabian Peninsula which was “bragging about killing Americans and trying to recruit new supporters” on key tribal websites.

“Within 48 hours, our team plastered the same sites with altered versions of the ads that showed the toll al Qaeda attacks have taken on the Yemeni people,” she said during a dinner at the Special Operations Command in Tampa, Florida.

State Department spokeswoman Victoria Nuland explained on Thursday that the Al-Qaeda ads featured pictures of coffins draped in American flags, whereas the US “counter-post” showed coffins draped in Yemeni flags.

The point was “to indicate that it is Yemenis who are dying at the hands of al Qaeda terrorists in Yemen,” Nuland added.

Clinton said the US effort is having “an impact, because we monitor the extremists venting their frustration and asking their supporters not to believe everything they read on the Internet.”

It is part of a broader effort by digital experts who are fluent in Urdu, Arabic and Somali who patrol the Internet and use social media to undercut Al-Qaeda propaganda and spotlight abuses committed by al Qaeda, Clinton said.

Nuland said the US message placed on the tribal sites amounted to a “counter-spoof” and did not involve hacking. “Whenever we do this... we identify ourselves clearly as part of the State Department's digital outreach team, so it's always clear who the sponsors of the alternative posts are,” Nuland told reporters.

“And let me also just make clear that we don't hack, we don't engage in covert activities, all of the work is attributed, as I said,” she said.

“In general, we usually do it on free sites and we do it in a free manner,”Nuland said.

In the case of posting messages on YouTube, she said, the United States pays for the service, just as everybody else.