Over the past two weeks there have been three worrying instances of the Angler exploit kit being used to infect website visitors with malware and ransomware. Cybercriminals are increasingly using exploit kits to deliver their malicious payloads and all organizations need to be aware of the risk.

Why AUPs May Not Be Sufficient to Keep Networks Secure

Many companies advise employees of the types of websites that can be accessed via work networks and which are forbidden. Typically, employees are banned from visiting pornographic websites, using the Internet for the sharing of copyright-protected material, installing shareware or other unauthorized software, and using unauthorized web applications and gaming sites.

Employees are provided with a document which they are required to read and sign. They are informed of the actions that will be taken for breaching the rules: verbal and written warnings for example, and in some cases, instant dismissal. These AUPs are usually effective and employees do heed the warnings if they value their jobs.

If an employee breaches the AUPs and accesses pornography for instance, action can be taken against that individual. It is probable that no harm will have been caused and the matter can be dealt with by HR.

However, if an employee breaches AUPs and visits a website that has been compromised with malware or installs shareware that includes malicious files, taking action against the employee will not undo the damage caused.

To better protect networks, AUPs should be enforced with a software solution. By implementing a web filtering solution, HR departments can ensure that inappropriate website content is not accessed, while IT departments can be prevented from having to deal with malware infections.

Even if AUPs are followed to the letter, malware may still be downloaded onto the network. The risk has recently been highlighted by two security incidents discovered in the past two weeks.

Legitimate Websites Compromised with Angler Exploit Kit

Last week, news emerged that a toy manufacturer’s website had been compromised and was being used to infect visitors with malware. The website had been loaded with the Angler exploit kit and was being used to silently infect visitors’ devices with ransomware.

An exploit kit is a malicious toolkit used by hackers to probe for security vulnerabilities in website visitors’ browsers. A visitor to a website containing an exploit kit – BlackHole, Magnitude, Nuclear, Styx, or Angler for example – will have their browser checked for out of date plugins such as Adobe Reader, Silverlight, Flash, or Java. If the plugins are not up to date, security vulnerabilities can be exploited to download a payload of malware. These attacks are silent and the website visitor will be unaware that their machine has been compromised.

This week, two more websites were discovered to have been hijacked and were being used to direct visitors to the Angler exploit kit. These websites were much more likely to be visited by company employees. They were the sites of two CBS-affiliated TV stations: KMOV in St. Louis and WBTV in Charlotte, North Carolina.

These news websites would be unlikely to be banned in AUPs, and few organizations would see the risk of their employees visiting these websites.

News Websites Contained Malvertising Directing Users to the Angler Exploit Kit

While the toy manufacturer’s website was directly infecting web visitors, in the case of KMOV and WBTV the attackers were using a common technique called malvertising. The websites had not been loaded with the Angler exploit kit, instead the attacks were taking place via third party adverts that were being served on the sites.

The sites contain adblocks which were used to serve advertisements via the Taggify network – a legitimate advertising network. However, a rogue advertiser had got around the controls put in place by Taggify and malicious adverts were being served.

The attackers hosted the malicious ad components – images and JavaScript- on their own servers. The malicious adverts were then served on unsuspecting website visitors. However, the rogue advertiser was also serving legitimate ads and these were displayed to web crawlers and scanners to avoid detection. Other users were served an advert that redirected them to the Angler exploit kit. If those visitors had browsers with out of date plugins, they would be infected with whatever payload the attackers chose to deliver.

Reduce Risk of Attack with a Web Filtering Solution

These three recent cases are just the tip of the iceberg. Criminals are hijacking all manner of websites and using them to host exploit kits. Legitimate websites serving third party adverts are also being targeted with malvertising.

Enforcing AUPs with a web filtering solution can help to prevent end users from visiting websites that have been compromised with malware. A web filter – such as WebTitan – can also be used to block third party advertisements from being displayed.

Unfortunately for enterprises, it is not possible to install patches as soon as they are released. Many patches require reboots, and that is not practical. The number of patches being released to plug security holes is considerable, and it takes time to patch all devices that connect to a network. Good patch management policies can reduce the likelihood of a successful attack, but they cannot prevent all attacks from taking place. If a web filtering solution is used that can block malvertising and websites known to contain malware, end users and networks will be better protected.