And just as the United States has begun an aggressive air campaign against the militants, Richard A. Stengel, undersecretary of state for public diplomacy, believes the United States has no choice but to counter the propaganda with a forceful online response.
"Sending a jazz trio to Budapest is not really what we want to do in 2014," said Stengel, referring to the soft-edged cultural diplomacy that sent musicians like Dave Brubeck on tours of Eastern-bloc capitals to counter communism during the Cold War. "We have to be tougher, we have to be harder, particularly in the information space, and we have to hit back."
The State Department division that Stengel heads has tried a range of approaches for engaging with the Middle East since 9/11, from slick, Madison Avenue-style ads to traditional international-visitors and exchange programs.
But now, digital operators at the State Department are directly engaging young people - and sometimes jihadis - on websites popular in Arab countries, publishing a stream of anti-Islamic State messages, and one somewhat shocking video, on Facebook or YouTube or Twitter, using the hashtag #ThinkAgainTurnAway.
Critics have questioned whether this effort is large, nimble or
credible enough. The United States' image in the Middle East - which seemed perched on the verge of hopefulness when President Barack Obama delivered a closely watched speech in Cairo in 2009 - is now at "the bottom of a sliding scale," said Lina Khatib, director of the Carnegie Middle East Center, in Beirut.
Stengel, who joined the Obama administration in February after seven years as managing editor of Time magazine, is focusing his efforts on an approach that reflects Obama's insistence that countries like Iraq must take responsibility for their own defense.
While Secretary of State John Kerry was assembling a military coalition against Islamic State, which is also known as ISIS or ISIL, on his most recent trip to the Mideast, Stengel met with Arab officials to create what he called in an interview "a communications coalition, a messaging coalition, to complement what's going on the ground."
The Center for Strategic Counterterrorism Communication is the State Department's spearhead in this fight and potentially defines the kind of pushback it would like to see friendly countries in the region engage in.
Formed in 2010 to counter messaging from al-Qaida and its affiliated groups, the interagency unit engages in online forums in Arabic, Urdu, Punjabi and Somali. It recently added English, making itself more transparent - and more open to critical scrutiny.
Posting on Twitter, Tumblr, YouTube and Facebook, members of the unit question claims made by Islamic State, trumpet the militants' setbacks and underscore the human cost of the militants' brutality.
Terror groups in Somalia and Nigeria are also targeted.
Recent tweets quoted Muslim scholars as saying "#ISIS murder of aid worker a violation of Islamic law" and described a Turkish nurse as "tired of treating #ISIS fighters so they can go behead people."
The tweets go out under the seal of the State Department.
When a Twitter user called Islam4Libya on Tuesday posted this: "Video emerging of #Children being killed in #Syria BY #US airstrikes, as if #Assad wasn't killing them fast enough," the "Think Again" feed quickly replied: "@ISLAM4L LIES: They say in the video that these children were wounded in Assad airstrikes. Stop recycling footage as anti-US propaganda."
The "Think Again, Turn Away" video mocks Islamic State, even briefly showing some of its beheaded victims. But some critics have questioned its deeply sarcastic tone: "You can learn useful new skills for the Ummah! Blowing up mosques. Crucifying and executing Muslims. Plundering public resources." (Ummah is Arabic for the Muslim community.).
The communication center's unofficial motto - "Contest the Space" - seemed to draw a high-level endorsement Wednesday when Obama, in his speech to the UN General Assembly, said the fight against extremism meant "contesting the space that terrorists occupy - including the Internet and social media."
With the State Department plunging deeper into the digital world, its Twitter accounts had nearly 2 million followers worldwide by last year, its Arab-language Twitter feed more than 200,000, and some ambassadors had Facebook followings in the tens of thousands.
Robert S. Ford, who recently retired as a diplomat from the State Department, said social media was indispensable to him when he was ambassador to Syria. Officials in Damascus "could shut my access off easily to Syrian media, but if I put something on Facebook it would be picked up by international Arab satellite media instantly, like Al-Jazeera, and that was going into Syrian homes very readily," he said.
Yet, the US digital effort led by the center has its limits. Of the more than 3,100 employees who answer to Stengel, only about 50 work for the counterterrorism communications center.
In contrast, Khatib said that an informant of hers in the Islamic State hotbed of Raqqa, Syria - a city hard hit by the latest US-led airstrikes - reported that Internet cafes there were "populated 24 hours a day" by many scores of young men "posting what the media department of the Islamic State wanted them to post."
She added that "the capacity of these kinds of groups far exceeds the capacity of any government, because these groups rely on thousands of members who are mobilized to engage in social media."
At one point recently, no tweets had gone out from "Think Again Turn Away" for 19 hours, even as jihadis generated a constant flow.
William A. Rugh, a former US ambassador to both Yemen and the United Arab Emirates, recounts that one US ambassador in an Asian capital had a popular Twitter account but needed four people to help him: one to clear content (which means delays), two to prepare the English and local-language versions of tweets, and another as webmaster.
"Social media is a blessing and a curse," said Rugh, author of the recent book "Front Line Public Diplomacy." "It's changed the environment quite a bit, but it's not a panacea."
And Bruce Gregory, a former director of the Public Diplomacy Institute at Georgetown University, said that there were "huge questions about how diplomatic actors representing the public interest engage in social media platforms with people in civil society who don't have those constraints."
Still, some observers contend that US digital diplomacy is learning its lessons, and gaining adherents and momentum. "Digital is definitely seen as one of the real US strengths" of recent years, said Jan Melissen of the Clingendael Institute in The Hague, who has written extensively on public diplomacy.
The impact of public diplomacy initiatives is nearly impossible to measure, specialists say. But one 2006 study of 394 students across the Middle East who listened to US-sponsored Radio Sawa or watched al-Hurrah television found that their views of US policy actually worsened slightly the longer they listened.
"If you try to manipulate people's perceptions, it can be counterproductive," said the study's author, Mohammed el-Nawawy of Queens University in Charlotte, North Carolina. "The very knowledge of being manipulated, of knowing you are being manipulated, can really backfire."
Stengel conceded that his department's programs were "not without risk." The center, he said, has no choice but to operate in "a difficult, alarming, disturbing space."
As to how to gauge success, Stengel said, "One thing you can't measure is, if you do prevent one young man from joining ISIL who would've otherwise massacred a thousand people, what is the value of that? You can't calculate that. You can't overestimate it."