By Mark Ward
BBC News Online technology correspondent
Legal experts are warning companies to do more to stop pornographic spam reaching employees.
Spam could see some firms land in court
Firms that do not take steps to stop sexually explicit spam could face lawsuits from employees suffering distress because of exposure to offensive images.
The experts urge companies to deploy anti-spam tools and curb offensive messages before they reach workers' desktops.
"This is an obvious case where employers are directly liable to their employees," said net law expert Dr Brian Bandey.
Dr Bandey said many firms tended to think of their duties to their staff in terms of statutes governing a healthy and safe workplace.
But, he said, there was a significant number of common law obligations and guidelines that also placed burdens on companies to look after their staff.
This common law requirement demanded that employers tackled all factors affecting a safe working environment, said Dr Bandey.
"This means all of the hazards, physical, mental and now emotional, that employees are exposed to," he said.
The obligation to oversee the welfare of workers extended to policing what reached the e-mail inboxes of workers and tackling sexual spam.
A survey this week by security firm Symantec found that 63% of the firms it questioned thought spam was offensive.
To avoid lawsuits for mental or emotional distress firms had to take all reasonable and practical steps to stop explicit spam, said Dr Bandey.
"But," he added, "many companies do not take these steps and I do not understand why they do not."
Dr Bandey said that some firms were already fighting legal claims that centred on the anxiety, emotional or mental distress caused by inappropriate words and pictures at work.
Ed MacNair, security manager at filtering firm NetIQ, said: "I think there no excuses now because the technology is available to stop spam coming in."
"Companies are being really slack," he said, "they are not addressing the problems."
Mr MacNair said now, on average, employees get 20 spam e-mails per day.
Image files soak up bandwidth and storage space
NetIQ analysis of the e-mail sent to one of its customers, an investment bank with 4,000 users, showed that 52% of inbound messages were spam.
Mr MacNair said that some of the spam was the fault of employees who had not been educated about responsible use of the net.
"The damage has been done," he said. "People have been promiscuous with their e-mail addresses and used them to log in to any and every type of website."
Many employees were also abusing net access and using work time to download and view pornographic and other inappropriate material.
Further analysis of the e-mail traffic to and from the investment bank showed that 9.8% of inbound e-mail contained image files and 95% of these image files were pornographic in nature.
On a typical day this meant that almost 9,000 pornographic images were being seen by employees.
These large image files used up 40% of the firms available bandwidth.
This cavalier use of the net could leave firms open to a second legal danger, warned Dr Bandey.
He said the growing trend towards holding firms criminally responsible for what their employees do could mean trouble for some companies.
"What's going to happen is that the police are going to wake up to corporate liability with respect to the transmission of pornography using corporate servers," he said.