Protesters from the Anonymous India group of hackers wear Guy Fawkes masks as they protest against laws they say gives the government control over censorship of internet usage in Mumbai, June 9, 2012. (REUTERS/Vivek Prakash)

BOSTON/CHARLOTTE, N.C. - Bank of America Corp, JPMorgan Chase & Co and U.S. Bancorp and other major U.S. banks seem to have stopped a group of hacker activists from seriously disrupting their online banking operations.

A financial services industry organization and several cyber security companies said a group of "hactivists" that impeded access to some major U.S. online banking sites in September had so far failed to gain traction in a second campaign that began this week.

"There has been no impact to critical financial systems," the Financial Services Information Sharing and Analysis Center, or FS-ISAC, said in a statement.

Tom Kellermann, vice president of cyber security at security software maker Trend Micro Inc, said the banks had been "very successful.

"I wouldn't see any prolonged outages for the major financial institutions in the coming year."

Arbor Networks, which sells equipment that companies can use to protect their websites against attack, said banks had bolstered their defenses since the last round of attacks in September.

"Everyone has been through this once or twice," said Dan Holden, an Arbor director. "There is just a better level of preparedness."

On Monday, a group that calls itself the Qassam Cyber Fighters said on a website called Pastebin.com that it was planning attacks against a group of five banks that also included PNC Financial Services Group Inc and SunTrust Banks Inc. The same group took credit for the disruptions in September.

U.S. Bancorp spokesman Tom Joyce said the regional bank's website was performing well, but some customers might be experiencing intermittent delays. "We can assure customers that their data and funds are secure," he said.

PNC said its website had unusually heavy traffic in the past several days, causing occasional difficulties in accessing it. Bank of America said it was monitoring its systems, which were operational.

SunTrust and JPMorgan declined to comment.