MBIA said it could not comment on the nature of the data breached.
Cutwater stopped managing pooled assets for Texas municipalities last year. Tom Jordan, chief executive officer of Public Trust Advisors, which took over management of the funds, is asking Cutwater to release more information but said the data is likely old and not of value to hackers.
Seely said he left numerous messages at MBIA and sent emails on the social media site LinkedIn. He said MBIA did not respond although it had read the emails sent over the social network and had visited his profile page.
"Based on the manner in which he was contacting people, including someone who hasn't worked for the company for the better part of 10 years, and the non-specific nature of his warnings of a problem with the MBIA website, the belief here was that he was attempting to sell us something," said Kevin Brown, a spokesman for MBIA.
Seely said he never asked for money or offered anything for sale.
MBIA only reacted when Seely contacted independent investigative reporter Brian Krebs, who specializes in cyber security issues. Krebs said he informed MBIA on Monday before blogging about the issue on his website, KrebsOnSecurity.com.
In a letter received by New Hampshire's banking department, Cutwater said the online system through which customers access their accounts, "appears to have been attacked," according to the letter, seen by Reuters.
"Thus far we have seen no evidence of any suspicious or improper transactions," though it is possible that information related to bank operating accounts or custodies may have been compromised, the letter said.