An as-yet-unpatched zero-day vulnerability affecting Internet Explorer is being abused much more widely than analysts had previously suspected.

The vulnerability first came to public attention last week with the Operation DeputyDog attacks against targets in Japan, as first reported by net security firm FireEye.

Websense, FireEye and AlienVault have since reported more malware-flinging campaigns exploiting this vulnerability. Several groups are using an exploit that takes advantage of security bugs in Microsoft's flagship browser software to attack financial institutions and government agencies in various countries in the far East, using various Trojans and similar strains of malware.

AlienVault discovered a version of the exploit hosted on a subdomain of Taiwan's Government e-Procurement System.

"When users visit the main webpage a Javascript code will redirect them to the exploit page if it is the first time they visit the page," the security firm warns.

Websense warned that a variety of hack-for-hire groups are exploiting the recently discovered “zero-day” vulnerability in Microsoft Internet Explorer to steal vital data from companies in the Asia Pacific region. These attacks are far more widespread than previously thought.

FireEye adds that various groups are involved in these attacks, even though in at least some cases they are using the same infrastructure but using it to push different malware, such as the PoisonIvy remote access trojan (RAT), and not the DeputyDog malware associated with the attacks against Japanese targets that first set off the alarm bells.

"Since we first reported on Operation DeputyDog, at least three other Advanced Persistent Threat (APT) campaigns known as Web2Crew, Taidoor, and th3bug have made use of the same exploit to deliver their own payloads to their own targets," write FireEye researchers Ned Moran and Nart Villeneuve in a blog post.

"It is not uncommon for APT groups to hand-off exploits to others, who are lower on the zero-day food chain – especially after the exploit becomes publicly available. Thus, while the exploit may be the same, the APT groups using them are not otherwise related."

"In addition, APT campaigns may reuse existing infrastructure for new attacks. There have been reports that the use of CVE-2013-3893 may have begun in July; however, this determination appears to be based solely on the fact that the CnC infrastructure used in DeputyDog had been previously used by the attackers. We have found no indication that the attackers used CVE-2013-3893 prior to August 23, 2013."

In related news, Rapid7 has added Internet Explorer exploit CVE-2013-3893 to Metasploit, allowing penetration testers and sysadmins to inspect systems for exposure to the vulnerability. But from the latest developments it appears it has gone mainstream.

Carl Leonard, senior security research manager EMEA at Websense, commented: "Websense estimates that close to 70 per cent of Windows-based PCs are vulnerable to this exploit. Given the huge attack surface, the actors behind these campaigns are racing to target companies before a patch becomes available."

"In addition, we anticipate that as more information of this zero day comes to light, the exploit will be weaponised and packaged into exploit kits rapidly, greatly increasing the number of attackers with access to this exploit," he added.

Websense advises sysadmins to install the Microsoft FixIt workaround as a safeguard against attack, pending the availability of a more complete patch from Microsoft. This will hopefully be available for the next edition of Patch Tuesday (8 October). ®