Symantec is crediting a hacker group with an impressive track record as responsible for finding the latest as yet unpatched vulnerability in older versions of Microsoft's Internet Explorer browser.
A gang Symantec calls the Elderwood group appears to have found the latest zero-day vulnerability in IE, which can allow a malicious website to automatically infect a person's computer.
Analysis of the attack code used to exploit the vulnerability has similarities to other code used by the Elderwood group to exploit other zero-day vulnerabilities in Microsoft's software, the company wrote on its blog.
In one example, Symantec found the phrase "HeapSpary" inside several samples of attack code.
"HeapSpary is a clear mistyping of Heap Spray, a common attack step used in vulnerability exploitation," the company wrote. "In addition to this commonality, there are many other symbols in common between the files."
In September, Symantec published a research paper saying that the Elderwood group appeared to have an "unlimited supply of zero-day vulnerabilities." A zero-day vulnerability is rare and highly valuable to hackers, as it means it has not been patched by the affected software vendor yet.
The Elderwood group may have possessed as many as nine zero-day exploits since 2009 when Symantec began first monitoring the group. Their attack codes have been distributed through targeted emails, known as spear phishing, and planted on hacked websites.
When someone with a vulnerable browser visits a hacked website, the malicious software is delivered. The Elderwood group has planted its malware on sites that indicate the group is targeting certain types of users, which Symantec calls a "watering hole" attack.
The Elderwood group appears to favour targets associated with defense contractors, human rights groups, non-governmental organizations and IT service providers, according to Symantec's September report.
Amnesty International's Hong Kong website was compromised in May 2012 in an attack linked to Elderwood, Symantec wrote.
An exploit for the latest IE vulnerability was found last month on the website of the Council on Foreign Relations as well as that of Capstone Turbine Corporation, a US-based manufacturer of gas microturbines used for power generation.
Microsoft issued a quick fix earlier this week for the IE software problem but will not distribute a patch for it on Jan. 8, the company's next scheduled patch release.