Estimation of Anti-Spyware Programs' Market Shares

Cookies Detected by Anti-Spyware Programs: The Current Status

Determining the effect of anti-spyware programs on cookies requires knowing which anti-spyware programs are most prevalent, so those programs' effects can be weighted accordingly. This appendix explains the methodology and results of my estimation procedure.

Unfortunately, there exists no single authoritative report of anti-spyware market shares.

• A recent NPD Group report covers market shares in security "distributor" sales. But NPD's data comes from "retailers, distributors, and other channel partners" -- omitting programs distributed by other methods, e.g. direct-to-consumer downloads.
• A Radicati report provides data about anti-spyware market shares. But Radicati covers only corporate installations, not individual end users.
• Even for electronic downloads, there exists no authoritative market share data. Download.com reports its top downloads, including PC Tools Spyware Doctor (15.4 million), Webroot (9.2 million), and Microsoft Windows Defender Beta 2 (2.5 million). But Microsoft claims 25 million active users of Windows Defender -- reflecting widespread distribution direct from Microsoft's web site, a channel not considered in Download.com's measurements.
• PC Pitstop surveyed its visitors' preferred anti-spyware aoftware. But these users' choices reflect their technical sophistication -- predictably, favoring free programs.

Combining these many reports is imprecise and error-prone, especially because they measure different quantities (retailer and distributor market share, versus downloads, versus active users). But most commonly reported are download / installation counts. The table below gives vendors' self-reported download / install count, where available. I then offer my anti-spyware market share estimates -- bearing in mind that some vendors (especially those offering free products) tend to have more downloads per active user, and that some vendor-provided figures include security suites that omit spyware protection.

	Vendor-Reported Download/Install Counts	My Market Share Estimate
Computer Associates PestPatrol	unknown	4%
LavaSoft Ad-Aware	130 million downloads	7%
McAfee Internet Security Suite	unknown	5%
Microsoft Windows Defender	25 million users	7%
PC Tools Spyware Doctor	50 million downloads	7%
Spybot Search & Destroy	unknown	7%
Sunbelt CounterSpy	unknown	2%
Symantec Norton Internet Security	50 million users	12%
Trend Micro Anti-Spyware	unknown	4%
Webroot Spy Sweeper	10 million users	7%
ZoneAlarm Internet Security Suite	35 million users	5%
(no anti-spyware installed)		33%

These estimates are imperfect, and I'm not thrilled with my methodology or with available data. But I know of no better source. Comments appreciated.