Viruses, worms, phishing and spam cause Canadian computer users plenty of stress, according to eMarketer, which cites a new survey released by Symantec and conducted by Pollara. The threat of virus infections (mentioned by 25 percent of adult users), slow performance or system crashes (24 percent), and spam (22 percent) are the three main factors that stress out online Canadians. But spam levels are actually down, according to Ipsos-Reid. By 4Q04, web users in Canada were on average receiving 87 spam messages per week, or 49 percent of their total emails, down from 134 in 2003, or about 68 percent of all emails.