Right off at the start: Have you used the Slipstream extension for Google Chrome to filter your Twitter stream? Do you still have it installed in Google Chrome? If so, then uninstall it at once!
There. I’m known for being somewhat long-winded in the wording, so I figured I’d better cut to the chase for once. Now for the long version.
I use Twitter, and for a time I used the “Slipstream” extension for Google Chrome in order to filter out certain posts that incessantly kept clogging up my Twitter feed mainly with notices from FourSquare and various movie rental sites about where people were and what they were watching (but I didn’t feel like unfollowing the people in question). Slipstream did the job pretty well, but after some time it went out of use, got discontinued by the developer (citing lack of user interest as their reason) and the extension simply stayed idle in my Chrome browser without me giving it a second thought.
That is, it wasn’t doing anything until yesterday (Tuesday, May 14th, 2013). All of a sudden, whenever I was on Twitter I would get redirected to a spam website which Norton Internet Security called “Web Attack: Facebook Fake Survey 9”, known as a phishing website. Norton also blocked the page, which leads me to think that it was somewhat serious. I also got various redirects to a porn site, which didn’t get blocked at all.
I tested Twitter in all my browsers (Firefox, Opera and Internet Explorer, in addition to Chrome), but was unable to replicate the problem in any of them. Conclusion: It had to be somehow Chrome-related.
I had a quick look through the installed Chrome extensions, which aren’t many, and Slipstream quickly stood out as the only likely suspect. I deactivated it and, behold, the problem disappeared. When I reactivated it to double-check, the redirects and Norton warnings returned.
My conclusion is that the old Slipstream extension has somehow gotten hijacked by people with nefarious intentions, enabling them to send previous Slipstream users to dubious websites whenever they are on Twitter. Not only is this a security hazard, but it makes Twitter almost impossible to use. The old Slipstream website, plugin.slipstre.am, has been discontinued, and appears to redirect to porn websites. Do not go there!
My advice: Uninstall the Slipstream extension without delay.