President Trump has routinely communicated with his personal lawyer, Rudolph W. Giuliani, and other individuals speaking on cellphones vulnerable to monitoring by Russian and other foreign intelligence services, current and former U.S. officials said.

Phone records released this week by the House Intelligence Committee revealed extensive communications between Giuliani, unidentified people at the White House and others involved in the campaign to pressure Ukraine, with no indication that those calls were encrypted or otherwise shielded from foreign surveillance.

The revelations raise the possibility that Moscow was able to learn about aspects of Trump’s attempt to get Ukraine to investigate a political rival months before that effort was exposed by a whistleblower report and the impeachment inquiry, officials said.

Trump is not identified by name in the House phone records, but investigators said they suspect he may be a person with a blocked number listed as “-1” in the files. And administration officials said separately that Trump has communicated regularly with Giuliani on unsecured lines.

“It happened all the time,” said one former senior aide, who noted that Giuliani had a range of foreign clients.

The disclosures provide fresh evidence suggesting that the president continues to defy the security guidance urged by his aides and followed by previous incumbents — a stance that is particularly remarkable given Trump’s attacks on Hillary Clinton in the 2016 presidential campaign for her use of a private email account while serving as secretary of state.