Internet Security Systems' (ISSX) first-quarter earnings fell slightly, but the company said second quarter and full-year results would be in line with analysts' estimates.The Internet security software maker said after the close Monday that net income for the first quarter rose to $5.22 million, or 10 cents a share, from $5.36 million, or 11 cents a share, a year earlier. Revenue rose 13% to $67.1 million from $59.5 million last year. Excluding the impact of noncash acquisition expense for amortization of intangibles and acquisition-related compensation charges for unvested stock options, the company's earned $6.35 million, or 13 cents a share, essentially flat with a year earlier. On that same pre-item basis, analysts were expecting Internet Security to earn 14 cents a share. For the second quarter, the company expects to earn 9 cents to 13 cents a share on revenue of $66 million to $70 million. Excluding items, Internet Security anticipates it will earn 12 cents to 16 cents a share, bracketing analysts' consensus estimate of 15 cents a share. The company continues to expect full-year earnings of 48 cents to 55 cents a share on revenue of $275 million to $285 million, but lowered its anticipation for earnings before items to 58 cents to 66 cents a share, below its previous estimate of 60 cents to 67 cents a share. Analysts were expecting the company to earn 63 cents a share on the pre-item basis. Internet Security shares were down recently nearly 8%, or $1.39, to $16.40, after closing the regular session off just 16 cents to $17.79.