The number of viruses transmitted by emails dropped to a record low in June, but spam is becoming an increasing problem for businesses, according to research published this week. Separate research carried out by research firm Vanson Bourne on behalf of Business Systems Group shows that 53 per cent of UK businesses rate junk email as the most pressing email security threat — almost twice the urgency given to virus protection. Rather than sending a virus in an email, malware writers now send spam emails with links to malicious web sites, which download viruses to users’ PCs.