Technology companies on Wednesday received troubling news that some had feared for years: Intellectual Ventures LLC has started suing.

The secretive firm co-founded by former Microsoft Corp. Chief Technology Officer Nathan Myhrvold has raised $5 billion to amass thousands of patents over the past decade.

Unlike most specialists in the field, Intellectual Ventures has avoided litigation, persuading big tech companies to become investors in his firm–along with payments that sometimes came to hundreds of millions of dollars. But Mr. Myhrvold never ruled out lawsuits if negotiations failed.

But on Wednesday, Mr. Myhrvold's firm, unable to secure payments from nine companies, announced three patent-infringement suits. One suit names the best-known players in security software–Symantec Corp., McAfee Inc., Trend Micro Inc. and Check Point Software Technologies Ltd.

Read the full Wall Street Journal article, “Big Patent Firm Sues Nine Tech Firms.”