LOS ANGELES -- Shaken after two consecutive losses and the dismissal of its coach, unranked USC needed more than a morale booster. It needed a victory.

Sparked by the defensive play of freshman linebacker Cameron Smith, USC knocked No. 3 Utah from the unbeaten ranks in front of 73,435 at the Coliseum.

Smith, a true freshman who enrolled early at USC and won a starting job in his first season, took his game to another plateau, intercepting three passes to spark USC to a 42-24 victory.

The win boosted USC's overall record to 4-3 and evened its Pac-12 South record at 2-2. Utah suffered its first loss of the season, falling to 6-1 overall and 3-1 in the Pac-12 South.

"That was a great victory for us tonight," interim USC coach Clay Helton said.

It was more than that. It was a morale boost for a program that was reeling from two consecutive losses and the dismissal of former head coach Steve Sarkisian.

Considering the caliber of opponent, the Trojans turned in their best defensive performance of the year. USC held Utah to 353 total yards. The Utes came into the game averaging 42.7 points in its previous four games.

Utah running back Devontae Booker was averaging 165.2 all-purpose yards per game, which ranked ninth in the country, and 130.5 rushing yards per game. With senior defensive end Greg Townsend Jr. leading the way, USC held Booker to 111 all-purpose yards (62 rushing, 49 receiving).

"Obviously, we're disappointed to lose the game," Utah coach Kyle Whittingham said. "In my opinion, that's the best team we've played all year, certainly from a personnel standpoint."

Smith had a rare 100-yard return game by a non-kick return specialist. He returned one interception 27 yards and another 41 yards and had a 54-yard touchdown in the second quarter.

"We've seen it through the spring," Helton said. "He's one of the more intuitive kids we've seen. He's playing on a very, very high level. It's unbelievable for a freshman."

Utah quarterback Travis Wilson completed 24 of 36 passes for 254 yards and two touchdowns. But he was stung badly by Smith's three interceptions. Wilson also was sacked three times.

Utah's most effective offensive player was true freshman wide receiver Britain Covey, who caught seven passes for 129 yards and two touchdowns. Covey added 88 yards in punt and kickoff returns to finish with 217 all-purpose yards.

"They played good defense and had a lot of great athletes on their team," Wilson said. "I need to make smarter decisions."

USC's offense did its part in support of the defense. Senior quarterback Cody Kessler connected on his first nine passes and finished 21 of 28 for 264 yards. His touchdown pass was a 26-yard strike to sophomore wide receiver JuJu Smith-Schuster, who had eight receptions for 143 yards -- his fifth 100-yard receiving game this year.

"We still have some things to clean up," Helton said. "When they play together like they did tonight, they're a good football team, they're hard to beat."

NOTES: USC sophomore Adoree' Jackson did not start at cornerback for the first time this year. Jackson made his first career start at wide receiver. He subsequently came in on defense later in the first quarter. Utah kept a watchful eye on Jackson, who caught six passes for only 37 yards. He also was a non-factor on punt and kickoff returns with a combined 32 yards. ... Utah sophomore LB Gionni Paul led all tacklers with 17 stops. That included 11 solo tackles, a sack and 5 1/2 tackles for loss. ... USC true freshman RB Ronald Jones II added to his team-leading rushing total by running for 73 yards on 15 carries. That included an 18-yard touchdown in the second quarter.