From this:

Obama's top terrorism and intelligence adviser, John O. Brennan, heads a firm (The Analysis Corp) that was cited in March for breaching sensitive files in the State Department's passport office, according to a State Department Inspector General's report released this past July.

...During a State Department briefing on March 21, 2008, McCormack confirmed that the contractor had accessed the passport files of presidential candidates Barack Obama, Hillary Rodham Clinton, and John McCain, and that the inspector general had launched an investigation.

Sources who tracked the investigation tell Newsmax that the main target of the breach was the Obama passport file, and that the contractor accessed the file in order to "cauterize" the records of potentially embarrassing information.

That would need to be confirmed, and I'm leaving looking into this up to you. There are several links about this here, a recent news report here, a September 2008 news release about one of the cases at justice.gov/opa/pr/2008/September/08-crm-841.html, the original Washington Times news report here, and a Washington Post story from December here.

Unfortunately, there were several people accessing several records and it's not really clear to me who was working for whom and what they accessed. Note that one case involved what might have been nothing more than credit card fraud, and one of the perpetrators of that confessed and was later shot in Washington DC. It's also an open question whether any of these employees had read/write access to passport files, or whether they were limited to simply reading the information without modifying it. Even though the original WashTimes article mentions that possibility that the records might have been altered, that would need to be confirmed when one knows which systems they accessed.