During the spring and summer months, credit card issuers have been doing what they won’t be able to do six months from now: boosting rates charged on existing credit card balances and new purchases.

A new federal law restricts new rate increases on existing card balances and modifies a number of other costly bank practices.

The banks, which need to make all such changes no later than Feb. 22, are shoring up revenue while the getting is still good. Posing as potential new customers and checking with bank Web sites and services, surveyors representing the nonprofit group Consumer Action learned that several months ahead of the law’s effective date, major banks had made all of the following changes:

-Bank of America (Stock Quote: BAC) added 3.25% to its minimum APR for purchases on its variable-rate Platinum Plus Visa card, taking its lowest rate of 6.99% to 10.24%.

-Capital One (Stock Quote: COF) increased its penalty rate for missed payments or other defaults by 6.25%, bringing the interest rate to 29.4% on its variable-rate Standard Platinum and No Hassle Miles cards.

-Citibank (Stock Quote: C) has increased purchase APRs on three variable-rate cards surveyed (Platinum Select Master Card, Diamond Preferred Rewards and AT&T Universal Savings) by between 2.25% and 3.25%.

Some issuers are hiking rates across the board while others are raising rates and adjusting terms for specific customers, observes Linda Sherry, director of Consumer Action's Washington office. Sherry said that while many banks implemented increases shortly before the Credit CARD Act of 2009 was signed, other institutions including Bank of America, Capital One, Citibank, US Bank and Wells Fargo (Stock Quote: WFC) continued raising rates in May and June when Consumer Action finalized its findings.