As mentioned previously in Spyware and Trespass, spam can, in principle, properly be considered a type of trespass—since it is a means by which the spammer uninvitedly uses another's property. As noted, a classic case is CompuServe v. Cyber Promotions, which held that transmitting a substantial volume of unsolicited e-mail to someone's computer, after demands to cease and desist, gives rise to a claim for trespass to personal property. And a court in Chicago recently a while back that the doctrine of trespass to chattels also "applies to the interference caused to home computers by spyware."
Just recently, as noted by Cyberlawyer Eric Sinrod, a Los Angeles court has ruled "that trespass was a viable legal theory to address the alleged distribution of spyware and adware programs."
The old common law doctrine of trespass to chattels relates to the interference with or taking of another's personal property. The idea is that this doctrine is flexible enough to cover various types of ways that others access or interfere with others' computers, networks and servers, without consent.
In the case of spam—unsolicited email—sending a large amount of unsolicited email to someone's computer can bog it down, fill up the hard drive, etc., thereby causing a sufficient amount of interference or harm to make a trespass claim. In the case of spyware or adware, the argument is that a user downloads something like a free game or screensaver, which causes the installation of spyware and adware on the PC without the user's knowledge or consent, which then "substantially impair" the ability of the computer to function (i.e. reduced its efficiency), and destroy other software on the PC, etc.
As Sinrod noted, there are eBay in 2000 also was able to convice a judge that the unconsented-to use of "spiders" by Bidder's Edge (an Internet auction aggregation site) to "crawl eBay's servers to obtain auction information ... placed some minimal burden on eBay's servers," so that eBay "prevailed on its trespass to chattels theory."
