My Answers Straight from the Spybot S&D 1.6.2 ( newest version ) help guide and FAQs.
Spybot - Search & Destroy is an on-demand spyware and malware scanner. That means it scans for threats whenever you choose to do so. It also offers some preventive measures like its Immunize function.
Resident, of which TeaTimer is a part, is Spybot-S&D's permanently running partner that does on-access scanning. This means that it will instantly detect and counteract to threats and unsolicited system settings changes.
Spybot-S&D Resident watches all applications that are being started on your computer. It knows the same bad files as the on-demand scanner of Spybot-S&D, and if it encounters an application that is known as a threat, it will automatically terminate this application.
What is the Resident TeaTimer? FAQ #033
The Resident TeaTimer is a tool of Spybot-S&D which perpetually monitors the processes called/initiated. It immediately detects known malicious processes wanting to start and terminates them giving you some options, how to deal with this process in the future. You can set TeaTimer to:
be informed, when the process tries to start again
automatically kill the process
or generally allow the process to run
There is also an option to delete the file associated with this process.
In addition, TeaTimer detects when something wants to change some critical registry keys. TeaTimer can protect you against such changes again giving you an option: You can either Allow or Deny the change.
As TeaTimer is always running in the background, it takes some resources of about 5 MB.
Which browsers does Spybot-S&D support? FAQ #048
Spybot-S&D does support many common browsers. As for resident protection, Spybot-S&D contains the Resident TeaTimer which is completely browser independent. It is a Spybot-S&D tool perpetually monitoring the processes called/initiated. In addition, TeaTimer detects changes to some critical registry values.
Spybot-S&D supports detection in cookies, history, start & search pages and bookmarks of these browsers plus cache for Internet Explorer and Opera (all following links are online links):
Firefox pre-0.9, 0.9, 1.x, 2.0 and compatible, including old Firebird variants
Microsoft Internet Explorer 5.0, 5.5, 6.0, 7.0
Netscape Communicator 4.x, 6, 7
Opera 4.x, 5.x, 6.x, 7.x, 8.x, 9.x and compatible
Thunderbird 1.x and compatible (where applicable)
My theory Spybot S&D is worth the time as it has found Trojans and cookies and some not to my consent tool bars ( Plugins ) installed on Mozilla that even Avast, AVG, Norton missed which caused rapid tracking cookies on Mozilla Firefox. I do recommend that you use Spybot S&D as it helps a lot but its your choice.