BEDFORD, Mass. — Cybercrooks continue their focus on credit unions, according to a monthly report from a leading Internet security firm.

RSA Security's antifraud command center, a 7/24 monitoring and takedown operation, said that 42% of American credit unions were targeted in March, compared with 35% of regional U.S. banks and 23% of nationwide banks.

Meanwhile, the so-called Rock Phish gang continues to drain tens of millions of dollars from bank accounts globally, RSA said, and accounts for more than 50% of phishing attacks worldwide.

The group uses a variety of well-known techniques in combinations that have helped it infiltrate thousands of e-mail servers, RSA said.

The company said that globally, 225 brands were attacked in March, a new record as phishing spread across new verticals and geographical regions. There was a 10% increase in U.S. banking brands attacked in March over February and increases also were noted in Australia and New Zealand, RSA said.