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Further to our previous blog about the use of TinyURL to obscure malicious links, a family member drew my attention to a problem she was having with the TinyURL site. Every time she tried to access a TinyURL link, she got a page advertising security products. (She was using their free firewall.) It turned out, though, that this wasn’t an ugly (and probably illegal) advertising ploy by the vendor.
Since the person was a (close) family member, the first thing I did was to replace her firewall (and a free antivirus product they were also using) with our own security suite. But the problem didn’t vanish. However, it now became clear that it wasn’t the firewall that had caused the issue, but the antispyware toolbar that is, by default, installed at the same time. It was blocking access to the TinyURL site because TinyURLs are used to conceal malicious sites and downloads.
You might think that a little draconian, since lots of perfectly innocent, useful and even essential URLs are sent as TinyURLs, but I can see their point. The toolbar did offer a clickthrough option, but trying to use it just resulted in a connection time-out. Unfortunately, I couldn’t find a way to make an exception for the TinyURL, although there apparently is one in the full product.
So why am I telling you this?
David Harley BA CISSP FBCS CITP
Director of Malware Intelligence
Author David Harley, ESET