Parasite Invasion & System Hostage counter measures are unfortunately not a "1 Step-10 second-fix" everyone would like.
Try malwarebytes to clean up your system:
http://www.majorgeeks.com/Malwarebytes_Anti-Malware_d5756.html
SpywareBlaster for system wide, realtime protection:
http://www.snapfiles.com/Freeware/security/fwantispy.html
Wave after wave of money hungry advertising schemes are sweeping the entire internet.
Don't let the battalions of external parasites into your system in the first place by taking an active defense posture to stop these guys on the threshold and keep 'em out. These steps will help, but methods (vectors) constantly change.
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INTERNET EXPLORER: Tools> Internet Options> Privacy> Advanced:
here check 'Override automatic....'; 'Allow session cookies'; 'Allow 1st party cookies' & 'Block 3rd Party Cookies'.
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FIREFOX: Tools> Options> Privacy: Check 'Accept Cookies from sites'
& Un-Check 'Accept 3rd Party cookies'
Firefox add-on's
Flashblock: https://addons.mozilla.org/en-US/firefox/addon/433
>> "NoScript" for Firefox will stop a lot of these adware/spyware & hijackers; and is the single most important thing you can do to prevent malware <<
https://addons.mozilla.org/en-US/firefox/addon/722
Use this feature to block unwanted advertising re-direct:
With NS running, down on the far right corner is a blue 'S' with a red line through it: right click that> tick 'forbid -------' &/or mark as 'untrusted'.
(Ticking all may reduce interactive behavior; enable just enough to get what's necessary to view the page)
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Rouge malware and server based spyware are becoming indisitnguishable & may cause multi-symptom effects on your system.
And worst of all, this spy/adware, records your clickstream & builds a profile of you with advertising conglomerate jackals.
Requires "Opt Out" and requires EVERY browser on EVERY machine be done...
Google here: http://www.google.com/privacy_ads.html
Yahoo here: http://info.yahoo.com/relevantads/
NAI garbage here: http://networkadvertising.org/managing/opt_out.asp
DoubleClick poison here: http://www.doubleclick.com/privacy/dart_adserving.aspx
(List of 64 Yahoo! co-conspirator advertisers they inflict on users are listed here: http://info.yahoo.com/privacy/us/yahoo/thirdparties/details.html)
When installing ANY new application, check the EULA for 'Toolbars' and/or other crud they try to slip past ya'.
**Astonishing new development**
Get this: the 'New' Yahoo, by default, allows your "Yahoo! Contacts (or Addresses)" computers, to send to whatever 3rd party software they have on THEIR computer, information about you! Can you believe that!!?
This is something you must terminate ASAP.
Go to your Yahoo! Mail: near the "Welcome (your name)", tick the 'Profile' link; next page, upper right corner, tick 'Settings'; next page, near the bottom is the box to uncheck.
And the deterioration of trust with Yahoo! grows...it's pathetic.
Good luck. :)