Lavasoft has a good article on this. Here is a snip I received recently.
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about
:blank - Possible Browser Hijack Attempt?
By Åsa Karlssoon - Content Manager
When scanning with Ad-Aware the homepage about
:blank is presented as a
Possible Browser Hijack attempt in the scan results list and in the log
file. The reason for this is that about
:blank is used by several variants of
CoolWebSearch to hijack browsers. However, this does not necessarily mean
that your computer is infected with CoolWebSearch.
Ad-Aware will detect multiple objects related to CoolWebsearch if your
computer is infected with a variant of CoolWebSearch. If you have set your
homepage to about
:blank and Ad-Aware only detects the about
:blank Possible
Browser Hijack attempt it is most unlikely that your computer is infected.
If you have chosen about
:blank as your homepage, and don't have issues
with browser hijackers, you can prevent Ad-Aware from detecting about
:blank
in future scans by adding it to the Ignore list. Select and right click on
the item in the Scanning results list and select "Add selection to
ignore-list". This will not affect your safety; Ad-Aware will still detect
CoolWebSearch objects if your computer gets infected.
If you have CoolWebSearch on your computer and wish to remove it,
select ALL the CoolWebSearch items, including the about
:blank listings, in
the Scanning results list and click Next to remove them. CoolWebSearch can
only be removed if ALL objects are deleted.
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"Kent" <(E-Mail Removed)> wrote in message
news:2293101c45d7f$9b4dbf50$(E-Mail Removed)...
> Hi, I am wa computer professional and have been unable to
> solve my problem. About:blank has established itself as my
> home page and I have deleted it from my registry with
> regedit but it keeps coming back. It also has various pop
> ups attached to it and the even come when I change my home
> page to www.msn.ca or my passport homepage. Is this the
> spyware ads in my registry somehow overwriting my input???
> Any suggestions????HELP