The Syrian Electronic Army sent out a warning over Twitter earlier Tuesday that said, "If you have 'Viber' app installed we advise you to delete it."
The hacking group was claiming responsibility for both breaching Viber's database and defacing its Web site, according to The Hacker News.
Right after the breach, Viber's support page on its Web site displayed a banner that said "Hacked by Syrian Electronic Army" and a note that said "Dear All Viber Users, the Israeli-based 'Viber' is spying and tracking you." As of this writing, the banner is no longer up and instead a "403 Forbidden" message is displayed.
Viber is an app that lets users call and message via Wi-Fi for free. In May, it announced that it had more than 200 million users spread across 193 countries.
The company confirmed to TechCrunch that indeed its Web site was defaced but that sensitive user information was not stolen.
"Today the Viber Support site was defaced after a Viber employee unfortunately fell victim to an email phishing attack," Viber told TechCrunch. "The phishing attack allowed access to two minor systems: a customer support panel and a support administration system. Information from one of these systems was posted on the defaced page."
The Syrian Electronic Army is a hacking group that supports Syrian President Bashar Assad, and during the last year it has hacked a number of news sites and company Web sites. In May, it hacked into the Twitter account of the parody news site the Onion and it also recently got into the accounts of the Associated Press, NPR, CBS, the Guardian, and the BBC.
CNET contacted Viber for comment. We'll update the story when we get more information.