CUPERTINO, Calif. ( TheStreet) -- Security software specialist Symantec ( SYMC) missed analysts' first-quarter sales and profit estimates, as customers focused their attention on short-term contracts.

The Cupertino, Calif.-based firm brought in sales of $1.43 billion in the quarter, down from $1.65 billion in the same period last year, and below its own guidance of $1.45 billion.

Adjusted for currency and the extra week in the firm's fiscal first quarter, however, Symantec's revenue came in at $1.44 billion, although this was still below Wall Street's forecast. Analysts surveyed by Thomson Reuters had expected Symantec to post revenue of $1.49 billion.

Confronted with heightened competition and a tough economy, Symantec said that customer buying patterns have changed.

"On the enterprise side, the customers are spending on shorter-term contracts, and that did result in some reduced new license revenue," Symantec CEO Enrique Salem told TheStreet.com in an interview. " But our earnings came in within our guided range because we did a lot of expense management, and we expect that to continue."

Including a 3-cent benefit from the extra week, Symantec earned 34 cents a share on net income of $285 million, down from 40 cents a share and $342 million in the prior year's quarter, but in line with the low end of the company's guidance. Analysts, however, had forecast earnings of 35 cents a share.

On a diluted basis, Symantec earned 9 cents a share on net income of $73 million, down from 20 cents a share and $170 million in the prior year's quarter.

Symantec, which competes with McAfee ( MFE), Microsoft ( MSFT) and ArcSight ( ARST), is enjoying strong demand for its consumer products, according to Salem.

"The consumer products did well in the quarter," he said, explaining that consumer revenue grew 6% year over year, adjusted for currency.

On a GAAP basis, the software specialist expects revenue between $1.395 billion and $1.445 billion, and earnings between 14 cents a share and 16 cents a share. On a diluted basis, Symantec's sales guidance is between $1.4 billion and $1.45 billion and the firm expects earnings between 32 cents a share and 34 cents a share. Analysts surveyed by Thomson Reuters had forecast revenue of $1.5 billion and earnings of 36 cents a share.

Symantec shares plunged $1.34, or 7.77%, to $15.90 in extended trading.

Reported by James Rogers in New York