US Patent 7673342 Detecting e-mail propagated malware

An e-mail client serves to detect mass mailing malware by detecting if over a threshold number of addressees from within the address book of that e-mail client are being sent an e-mail or over a predetermined number of substantially identical e-mails are being sent by that e-mail client. A quarantine queue may be provided in which e-mail messages are held for a predetermined period prior to being sent out in order that separate e-mail messages being sent to a large proportion of the address book addressees may be identified and linked together.