Every FTSE 100 and Fortune Global 500 company has been targeted by typo-squatters, according to research by commercial law firm Pinsent Masons.
Typo-squatting is a form of cyber-squatting that exploits typing errors made by internet users when entering a company's website address into a browser.
Users are then taken to alternative websites, where they may be tricked into clicking on adverts for competing goods and services.
"Typo-squatting is dangerous to brand owners because competitors are using their brands to poach customers, but many companies are not doing anything about it," said John MacKenzie, intellectual property expert at Pinsent Masons.
MacKenzie said companies should allocate a slice of their budget to identify the scale of the problem. He said they should deal with typo-squatting automatically as part of the cost of doing business.
"It is more cost-effective to monitor typo-squatting routinely using various online tools, and have set procedures in place to deal with what amounts to copyright infringement, than to deal with the problem in an ad hoc fashion," he said.
Such procedures typically include sending letters to typo-squatters demanding that they cease and desist, which is surprisingly effective, MacKenzie said.
If that fails, the law provides adequate protection for companies to fight against typo-squatting, which is not considered to be an acceptable commercial practice.
Companies can easily check whether they are being targeted by typo-squatters by visiting the domaintools.com website, clicking on the "domain search" tab, and entering the company brand name to see if anything similar is used by typo-squatters.