Microsoft ( MSFT) has filed 15 antispam cases in the U.S. and the U.K. to help protect consumers, the company announced Tuesday. The lawsuits allege that the defendants collectively are responsible for flooding Microsoft's customers and its systems with more than 2 billion deceptive and unsolicited email messages, commonly referred to as spam. The company filed the actions under Washington state's stringent antispam law. Two other civil lawsuits were filed in the U.K., alleging the unlawful harvesting of email account names and other illegal spamming practices under the Misuse of Computers Act. The lawsuits are targeted at stopping some of the most offensive email practices. In some cases, defendants are alleged to have used deceptive and misleading subject lines to disguise email messages that contained pornographic images, dating-service solicitations and other adult services. One case involves email messages that include a false virus warning. Recipients are instructed to download an "update" purported to protect their system, when the download is actually a toolbar that appears to track their movements on the Internet. In other cases, defendants are alleged to have "spoofed" the sender's email address, making it appear that the spam originated from hotmail.com or other recognized senders, which could mislead recipients or circumvent antispam filters. Among the defendants are several individuals and entities that are listed as spammers on Internet registries. Microsoft also has begun to implement antispam features in its products.