Security...

When I turned the globals in php everything was fine.
People that keep blaming vBSEO alone they don't know anything about web servers.
As long as your web host hardened your server then you should be fine.
If you have a managed web host make sure they double check all server security options including firewall settings.

If you use cPanel/WHM make sure you have CSF enabled.

Also, do not install every single custom plugin you find out there, make sure you install plugins from a reputable company/person that has a good background.

Scan your website using the following link: http://sitecheck.sucuri.net (might not be the best way, but at least it's something)

If you run an unmanaged vps/dedicated server then you should hire someone to help you protect your server against malicious attacks.

Again, before jumping the ship, you should definitely check your server!

FYI I used the http://sitecheck.sucuri.net check and it didn't find anything even though one of the sites was still having the redirect issue.

What did make it go away was the vbseo_checkplugins file that I ran. After I did that, my traffic immediately went back up.

Glad to hear that.

If you keep the server security and the forums up to date, as well as vBSEO and any other addon you'll avoid almost all the problems related to the security

Rafael

Stanger you have to check twice with the Sucuri scanner (cache results... you know).

But after register_globals off (and other security things)... a few weeks scanning almost every day and 0 problem, unless a new undetectable malware appears again... but the famous "url123" its gone.

I'm glad to hear that the issue is no longer reproducible on your site, Diego