Shares of

Internet Security Systems

(ISSX)

bounced back from a downward slide Tuesday after the intrusion-detection software maker reported first-quarter net income shrunk by about 50% from a year ago, while pro forma earnings still met analyst expectations.

Shares of the heavily shorted Atlanta software maker closed down $1.12, or 4.8%, at $22.03. After markets closed, ISS shares were trading at $23.21.

The company reported net income of $3.4 million, or 7 cents a share, on $58.4 million in revenue. That compares with net income of $6.5 million, or 15 cents a share, on $61.2 million in revenue in the same period a year earlier. Excluding charges, the company reported pro forma net income of 10 cents a share, down from 15 cents a share in the year-ago period.

Wall Street was expecting the company's pro forma earnings to remain sequentially flat at 10 cents a share, and revenue to increase a modest 2.7% to nearly $60 million, according to Thomson Financial/First Call.

For the second quarter, ISS said it expects to report revenue ranging from $60 million to $62 million and pro forma earnings ranging from 11 cents to 12 cents a share. Wall Street is expecting earnings of 12 cents a share on $64 million in revenue.

For the full year, ISSX updated guidance to the low end of its previous revenue target of $260 million to $270 million and pro forma earnings of 55 cents to 60 cents a share. The consensus on Wall Street was for full-year earnings of 55 cents a share on revenue of $264 million.