WASHINGTON — Defense Department counterintelligence investigators suspected that Iranian exiles who provided dubious intelligence on Iraq and Iran to a small group of Pentagon officials might have ‘been used as agents of a foreign intelligence service … to reach into and influence the highest levels of the U.S. government,’ a Senate Intelligence Committee report said Thursday. A top aide to then-secretary of defense Donald H. Rumsfeld, however, shut down the 2003 investigation into the Pentagon officials’ activities after only a month, and the Defense Department’s top brass never followed up on the investigators’ recommendation for a more thorough investigation, the Senate report said. The revelation raises questions about whether Iran may have used a small cabal of officials in the Pentagon and in Vice President Dick Cheney’s office to feed bogus intelligence on Iraq and Iran to senior policymakers in the Bush administration who were eager to oust the Iraqi dictator. Iran, which was a mortal enemy of Iraqi dictator Saddam Hussein and fought a bloody eight-year war with Iraq during his reign, has been the primary beneficiary of U.S. policy in Iraq, where Iranian-backed groups now run much of the government and the security forces. […]