I've been using Spybot S&D since longer than I can remember. It's really excellent software, and I'm genuinely impressed that it's offered free to the public. Everybody I know also uses it, too!
But there's something that puzzles me and that I cannot REALLY answer well. I get asked about this often, and I'd appreciate hearing how others answer it.
As with all of my security programs, I run similar programs. Basic redundancy.
In the case of Spybot S&D, the twin program in AdAware.
Both Spybot and AdAware check for something like 350,000 bots (and maybe others, too). I run them both each week on each computer.
Spybot needs about an hour and runs my computer in excess of 50% of its CPU capacity. AdAware runs in about 20 minutes and never runs the CPU up over 20 or 25%. Originally, I just assumed that Spybot was covering a lot more ground, but I always select the most thorough, comprehensive scan options for these programs.
Frankly, I cannot figure out why Spybot runs so long and hot. I usually suggest that it must be searching more thoroughly, but, frankly, that's just spin. The correct answer here is that I don't know.
[As for search results, I don't think either Spybot or AdAware has found anything on my personal machine other than the MRIs generated by my own software. On other machines that I've been asked to review, Spybot and AdAware have earned their keep equally. Oddly, they *never* both find the same bot.]
Thanks for your time with this.
And, about the original suggestion I mentioned, . . . I'd suggest that the folks at Spybot include a bit of the explanation as to what-all is going on that demands the high relative computer usage.