NBC News on Thursday corrected its report that federal agents had placed a wiretap on phone lines associated with President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE’s personal attorney, Michael Cohen.

The news outlet updated its initial report to reflect that Cohen’s phones were subject to a "pen register," which allows investigators to create a log of phone calls associated with Cohen’s number.

Its original story, which reported the wiretap, cited two separate sources with knowledge of the proceedings. However, three senior U.S. officials later disputed the report, prompting the correction.

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"Correction: Earlier today NBC News, and this reporter, said that Michael Cohen's phone lines were wiretapped. 3 Senior U.S. Officials now dispute that, saying the monitoring was limited to a log of calls (pen register) not a wiretap of Cohen's lines. We will continue to report," one of the story's reporters, Tom Winter, tweeted following the correction.

Correction: Earlier today NBC News, and this reporter, said that Michael Cohen's phone lines were wiretapped. 3 Senior U.S. Officials now dispute that, saying the monitoring was limited to a log of calls (pen register) not a wiretap of Cohen's lines. We will continue to report. — Tom Winter (@Tom_Winter) May 3, 2018

The distinction is significant. The use of a pen register allows investigators to track incoming and outgoing calls from a number, whereas a wiretap allows investigators to actually listen in on calls.

Josh Blackman, a constitutional law professor at the South Texas College of Law in Houston, said it’s far easier to obtain a pen register than a wiretap.

“While the latter records phone calls and captures private information, the former only tracks phone numbers dialed,” he said. “The Supreme Court has recognized that by dialing a phone number, a person voluntarily shares that information with the phone company, so there is a reduced expectation of privacy."

Glen Kopp, a partner at Mayer Brown and former assistant U.S. attorney for the Southern District of New York, added that pen registers are fairly common in investigations.

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“A judge has to approve the use of a pen register, but the hurdles for obtaining approval are way less than for a wiretap of someone’s telephone,” he said.

NBC originally said that at least one phone call between the White House and a line associated with Cohen was monitored. It has since updated its story to note that one call was logged.

The initial report sparked outrage from Rudy Giuliani, who represents President Trump in the Russia investigation.

"I am waiting for the attorney general to step in, in his role as defender of justice, and put these people under investigation,” Giuliani told The Hill.

The former New York City Mayor added that wiretapping Cohen's phone would amount to “gross misconduct” by the government.

The White House did not have any comment on the story when it was brought up at Thursday afternoon's press briefing.

Lydia Wheeler contributed.