Experian Group Ltd., one of the three major credit bureaus, announced Thursday that it has filed suit against personal data security firm LifeLock Inc. According to Experian, LifeLock's practice of placing fraud alerts on its clients' credit files in an attempt to safeguard them is misleading and fraudulent. Experian contended that LifeLock's actions have damaged Experian and consumers while also threatening to undermine the effectiveness of fraud alerts. The damage amount of the lawsuit, which was filed in the U.S. District Court for the Central District of California, was not disclosed. Venture-backed LifeLock is headquartered in Tempe, Ariz.