FORTUNE -- Buying patents and suing companies for violating them is a large and growing business, and nobody has felt its impact more than Apple (AAPL).
Of all the companies sued over the past five years by so-called non practicing entities (NPEs) -- a.k.a. "patent trolls" -- Apple got hit the most: 171 patent lawsuits as of June, according to PatentFreedom, a community of companies that tracks the activity of 710 parent NPEs and their 2,500 subsidiaries and affiliates.
Among the fattest targets, Apple was followed by Hewlett-Packard (137 lawsuits), Samsung (133) and AT&T (127). (See list below.)
The targets of these lawsuits tend to view patent trolls as technological parasites. NPEs, by definition, don't actually manufacture anything. Instead, they either develop a process and patent it, or they buy or license the patents from others.
"Ultimately, a patent is nothing more or less than a license to sue someone," Michael Brody, an intellectual property specialist at Winston & Strawn, told an audience at Stanford University earlier this week.
An account of Brody's talk posted Wednesday by TechHive's Mark Hachman is packed with trollish facts and figures:
"That's a good business to be in," says Brody. "And that's why a lot of people are in it."
Below, PatentFreedom's list of the most pursued companies.
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