Natural Viagra and financial stings most common junk email...The most prevalent spam attacks of 2001 have been revealed, with porn-related junk mail a surprise omission from the top three. According to anti-spam firm Brightmail, the biggest hit this year was an advertisement for a natural alternative to male impotence drug Viagra. The second most common unsolicited mail was a financial scam asking recipients for money and purporting to be from the legal adviser to a former Nigerian Army Chief. In third place was an email exploiting the 11 September tragedy. Marten Nelson, business development director for Brightmail, said: "This alone tells us all we need to know about spammers - they are utterly unscrupulous, willing to use any event to their advantage." Nelson said there are a number of ways to try and avoid receiving spam. "Don't ever respond to spam, even if just to ask the sender to take you off his list - spammers treat this as a proof that your address exists, and you will just receive more," he said. He also warned users to steer clear of chat room or discussion groups where email addresses are freely available. Brightmail estimates between 15 and 30 per cent of emails handled by ISPs are spam.