Cockroaches: everyone hates them but nobody knows how to beat them.
Mine always materialise in the bathroom and I can never work out whether they enter via the window, the plughole or the front door. Worse, whether I spray them, stamp on them or chuck them out of the window, they always return, just like spam.
Except that, in fact, spam is even more persistent. This virtual plague of unasked for and unwanted messages comes at me more or less continuously, promising a VIP credit card, a no-questions-asked loan or just irresistible sexual magnetism.
Googling for a solution to the deluge, I have discovered a potentially lethal weapon tipped by the Massachusetts Institute of Technology's Technology Review and touted by commercial carrier Cloudmark as offering a 94 per cent spam reduction rate.
It is called Vipul's Razor.
This peer-to-peer spam-tracking database works by identifying the signatures - brief but unique textual features - in spam messages. Then, since your average spammer zings the same message at thousands of people, Razor disrupts this procedure by enabling the first recipient to add it to the database, at which point everyone else automatically blocks it. Assuming in each case the initial recipient blacklists correctly, the Razor just gets sharper and sharper.