A watering hole attack targeting the US Department of Labor (DoL) website served an exploit that took advantage of a previously unknown vulnerability in Internet Explorer 8.
Following an advisory issued on Friday warning that attackers were actively exploiting a remote-execution zero-day flaw in IE8, Eddie Mitchell, security engineer at Invincea, said in a Friday blog post that this is the vulnerability that was being attacked on the DoL site. A malicious script on several of the pages directed victims to an attacker-owned site serving the Poison Ivy remote access Trojan.
The Labor Department said in a statement: "The website was immediately taken offline and the department began working with appropriate internal and external authorities to investigate and to mitigate any potential impacts.
“The website will remain offline until DoL completes its initial investigation. At this time, there is no evidence of compromise to or loss of DoL information.” The compromised DoL pages have been cleaned, but they remain offline.
Research by AlienVault found that in addition to the DoL website, at least nine other websites were redirecting to the malicious server at the same time, including several non-profit groups and institutes, as well as "a big European company that plays on the aerospace, defence and security markets".
Microsoft said in its advisory that Internet Explorer 6, 7, 9 and 10 were not affected by the vulnerability, and recommended users upgrade while it works to develop a security update to address this issue.
It recommended users set internet and local intranet security zone settings to 'high' to block ActiveX Controls and Active Scripting in these zones, and configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the internet and local intranet security zones.