Users who accessed some stories on the Reuters website Sunday were redirected to a message from hackers criticizing the news agency's coverage of Syria.
The attack was carried out by the Syrian Electronic Army (SEA), a hacker group that's publicly supportive of Syrian President Bashar al-Assad and his government and which has targeted various media organizations in the past, including IDG.
"Stop publishing fake reports and false articles about Syria! UK government is supporting the terrorists in Syria to destroy it. Stop spreading its propaganda," the rogue message seen by some Reuters.com visitors read.
According to a security researcher named Frederic Jacobs, SEA did not actually hack into Reuters' website, but injected the redirect code into it through a New York-based advertising network called Taboola.
"It is still unclear how Taboola was compromised but given SEA's track record, phishing would be my first guess," Jacobs said Sunday in a blog post.
The value of compromising Taboola is actually greater for SEA than compromising Reuters, because according to the ad network's site, it delivers its recommendations to 350 million unique visitors each month and has partnerships with high-profile media sites including Time.com, USA Today, the New York Times, BBC, TMZ, The Hollywood Reporter, Politico.com, Examiner and others.
Any of Taboola's clients could have been attacked in a similar way to Reuters, Jacobs said.
Taboola acknowledged being the source of the compromise and said that SEA hacked one of its widgets used on Reuters.com.
The security breach lasted from 7 a.m. to 8 a.m. EDT Sunday with no suspicious activity being detected after that time, Adam Singolda, Taboola's CEO, said in a blog post.
"While we use 2-step authentication, our initial investigation shows the attack was enabled through a phishing mechanism," Singolda said. "We immediately changed all access passwords, and will continue to investigate this over the next 24 hours."
SEA's preferred method of attack is spear phishing -- a targeted form of phishing. When the group doesn't succeed at compromising an employee from its targeted organization it goes after that organization's partners and various service providers.
In August 2013 SEA used spear phishing to compromise a reseller account at Melbourne IT, an Australian domain registrar and IT services company. The attack allowed the hacker group to alter the DNS (Domain Name System) records for several domain names including nytimes.com, sharethis.com, huffingtonpost.co.uk, twitter.co.uk and twimg.com and temporarily redirect those websites to a server under its control.
In February the group gained access to the administration panel of a San Francisco-based company called MarkMonitor that manages domain names on behalf of large enterprises. This allowed them to change the WHOIS information for facebook.com, changing the domain's contact address to Damascus, Syria.
In April, SEA managed to redirect users trying to access the RSA Conference website to a defacement page. The attack was carried out through Lucky Orange, a real-time Web analytics provider used by the RSA Conference website.
"If you're using 3rd party analytics or advertising networks, your website's security relies on the weakest of those since any of them is able to take over your website (and potentially steal your user's data or trick them into installing malware)," Jacobs said. "Websites like Reuters use more than 30 of these services and thus expose a considerable attack surface."