In every security forum, here's one argument you keep seeing. Ad-Aware or Spybot? Which is better at finding and removing unwanted software? There are staunch supporters of each, and both have valid reasons for their opinions.
Most support their opinions based upon experience. "The last time I ran Ad-Aware, I ran Spybot afterwards, and found stuff that Ad-Aware missed", or "Spybot never finds any bad stuff. Ad-Aware constantly finds bad stuff".
What you have to remember is that, although the two are competing products, they also are complementary products, and were developed for two different reasons. Ad-Aware was developed to find, and remove, adware; Spybot S&D was developed to find, and remove, spyware. Adware and spyware are not the same. Please bear in mind that these are classical comparisons; as time has passed, the two classes of malware have converged somewhat.
- Puts ads on your screen (or influences contents of ads).
- Generates incoming network traffic, containing the ad content.
- Intercepts information such as keystrokes (looking for account names and passwords), or watches what websites you surf.
- Generates outgoing network traffic, passing the intercepted information back to the spyware servers.
Both Ad-Aware and Spybot S&D look for bad software in different ways, based upon the traces their targets may be expected to leave. Different bad software (with differing inherent behaviour, and therefore differing detectable characteristics) requires different detection and removal techniques. There are, also, features that adware and spyware have in common (apart from being stuff that you don't want on your computer, and this too varies according to the needs of each computer owner).
- Both are generally loaded onto your computer because you connected your computer to the Internet.
- Both can be very hard to remove from your computer.
- Both may use protective mechanisms, that guard against deletion of the active components.
Based upon their different functionalities and purpose, adware and spyware, which are targeted products, may be more or less likely to be installed onto your computer when you access the Internet. Based upon differing Internet access, one person might expect to acquire more adware, and another person might acquire more spyware. People acquiring more of one or the other would then expect to see more detections by Ad-Aware or Spybot S&D.
Of course, if you use a layered defense, you may never see any adware or spyware. Just as the dentist finding no cavities in your teeth shouldn't lead you to stop brushing, though, your finding no malware shouldn't lead you to remove redundant protection.