NEW YORK ( TheStreet) -- Short sellers continued their second quarter assault on financial stocks, as bets against the sector rose 2% in the first half of June, according to research published Wednesday by Keefe, Bruyette & Woods. Short interest has risen in each reporting period in the second quarter for a total increase of 17.5%. Overall short interest, meanwhile, has increased 15.8% quarter to date, KBW's analysts found. The Financial Select Sector SPDR ( GWRE), a popular exchange-traded fund that tracks financial stocks, has fallen 10.58% during the quarter versus a 5.12% drop for the Dow Jones Industrial Average. Still, the rate of increase slowed considerably from the second half of May , when bets against financial stocks jumped faster than at any time since market hit bottom in March 2009. That surge, encompassing the period from May 15 through May 31, was driven by a 61% rise in short interest on "universal" U.S. banks Bank of America ( BAC), Citigroup ( C), Goldman Sachs ( GS), Morgan Stanley ( MS), and JPMorgan Chase ( JPM). This time around, however, short sellers focused on trust and custody banks, which saw an 18% rise in aggregate short interest, including a 67% jump for State Street Corp ( STT). State Street shares nonetheless managed to rise 6.4% in the first half of June versus a 2.5% increase for the S&P 500. Financial stocks seeing the biggest rise in short interest as a percentage of their overall float were Guidewire Software ( GWRE), which sells software to property and casualty insurers, and Springfield, Mass.-based United Financial Bancorp ( UBNK). Guidewire short interest rose 3.8% as a percentage of the float, while United Financial rose 2.7%. Short sellers borrow shares in the hope the stock will fall. They can then buy it back at a lower price and pocket the difference. The New York Stock Exchange releases short interest data twice a month with a roughly two week lag time. -- Written by Dan Freed in New York. Follow this writer on Twitter.