(CNN) -- One video shows more than 100 prisoners paraded across the desert in their underwear, then lying face down as militants unleash a hailstorm of bullets into their bodies.
Other images show crucifixions and public executions in towns overrun by terrorists.
And recent footage showing the beheading of a second American journalist proves that ISIS wants the world to know how brutal it can be.
The insurgents are experts at using footage of their crimes as propaganda to terrify those who disagree with their radicalism and to threaten foreign leaders. The visuals are as much a part of ISIS' terrorism as its bloody march across the Iraq and Syria.
In the video of American Steven Sotloff's decapitation, the executioner has a stern warning for the U.S. President:
"I'm back, Obama, and I'm back because of your arrogant foreign policy towards the Islamic State," the man says in the video, released just days after fellow journalist James Foley was beheaded.
"Just as your missiles continue to strike our people, our knife will continue to strike the necks of your people."
Even a 7-year-old child was photographed holding a severed head. The picture was reportedly taken in Raqqa, the ISIS stronghold in Syria, where the boy's Australian father had taken his family to join the fight.
Publicized beheadings had actually stopped in years past
A decade ago, al Qaeda -- the terror group that spawned ISIS -- made headlines with a series of decapitations, including those of Americans Nicholas Berg and Eugene "Jack" Armstrong.
That means the beheadings could continue.
But it's not just Western captives who fall victim. Last week, a Kurdish man was executed in front of a mosque in Mosul in a video called "A message written in blood," notes Charlie Cooper, Middle East researcher at the Quilliam Foundation.
But because that message "was directed at the President of Iraqi Kurdistan, this particular piece of propaganda did not receive widespread coverage in the international media," Cooper wrote in a piece for CNN.com.
"They have shown their willingness to kill anyone in their path -- not just Americans, not just Westerners, but Iraqis of all faiths, of all sects," U.S. State Department spokeswoman Marie Harf said. "They've shown their complete barbarism in doing that."
The media's role
Cooper said the media has a responsibility to treat ISIS propaganda carefully.
"Every time a still or clip from an ISIS video is shown, the group gets what it wants: the oxygen of publicity," he wrote.
"Of course, it is necessary that people the world over are aware of the atrocities occurring at the hands of ISIS, but journalists must be careful not to do the jihadists' job for them."
The decision on whether to publicize parts of the recent beheading videos have even divided journalists.
International broadcaster Al Jazeera said it had decided not to show any images of Sotloff from the video -- a more conservative position than other TV networks.
"We suggest all media do the same," Al Jazeera's public relations account said via Twitter, using the hashtag #ISISmediaBlackout.
And while the video has been blocked from various video sharing platforms, they have also reappeared as many times, Quilliam senior researcher Erin Marie Saltman wrote.
She said that kind of trend "once again emphasizes that the new frontline for counter-terrorist practitioners is online extremism."
Glossy recruitment tools
Part of the problem is the radicals are extremely tech- and media savvy.
"We are way behind. They are far superior and advanced than we are when it comes to new media technologies, social media, when it comes to video production qualities, and in disseminating their propaganda over the Internet," said Maajid Nawaz, a former jihadi and author of "Radical: My Journey out of Islamist Extremism."
Some videos used by the terrorists rival the production quality of Hollywood films.
One hourlong video shows a collection of bombings, executions, kidnappings and beheadings. As one roadside bomb blasts a vehicle into the sky, two men in the background of the video chuckle.
The recruitment tactics can be both blatant and subtle.
For about $10, supporters can buy a shirt with ISIS' logo and phrases such as, "We are all ISIS" and "Fight for Freedom, Until the Last Drop of Blood."
And it may be no accident that a militant with a British accent fronted the video of Foley's death.
That kind of tactic could inspire more foreign jihadists, a former ISIS fighter told CNN.
"It is possible that the goal was to project the image that a European, or a Western person, executed an American so that they can showcase their Western members and appeal to others outside Syria and make them feel that they belong to the same cause."
CNN's Nic Robertson, Brian Stelter, Mohammed Jamjoom, Anderson Cooper and Samuel Burke contributed to this report.