Browser user agent string with all 0s

Question

I've had 2 mac users hit my site today, and both their browser user agents were:

Mozilla/5.0 (000000000; 0; 00000 000 00 0 000000; 00000) DDDDDDDDDDDDDDDDDDDD DDDDDDD DDDD DDDDDD DDDDDDDDDDDDD DDDDDDDDDDDDDDD

instead of what I would generally expect. I contacted one of them and had them try FireFox and Chrome as well - same result. So clearly something (a proxy, most likely?) is stripping their useragent and replacing it with junk. They're not aware of any software running on their Macs which would do this.

Has anyone else seen this before? Any ideas what does this and how widespread it is?

Answer 1

A Google search for (user agent DDDDDDDDDDDDDDDDDDDD) suggests that the culprit is a program called Intego VirusBarrier. One of the features listed on its page is "Hides browser and platform information."

This behavior can be changed, according to this thread:

On my Intego VirusBarrier X6 I also discovered the tab "Information Hiding" under "Surf". I unchecked "Hide information about my computer and web browser" and it worked instantly.