<ARTICLE> 5
<MULTIPLIER> 1,000
<CURRENCY> US DOLLARS
       
                             
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1998
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               SEP-30-1998
<EXCHANGE-RATE>                                      1
<CASH>                                          40,540
<SECURITIES>                                   113,164
<RECEIVABLES>                                   30,635
<ALLOWANCES>                                       715
<INVENTORY>                                      8,214
<CURRENT-ASSETS>                               203,309
<PP&E>                                          25,705
<DEPRECIATION>                                       0
<TOTAL-ASSETS>                                 255,990
<CURRENT-LIABILITIES>                           31,343
<BONDS>                                              0
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                           414
<OTHER-SE>                                     221,669
<TOTAL-LIABILITY-AND-EQUITY>                   255,990
<SALES>                                        124,419
<TOTAL-REVENUES>                               124,419
<CGS>                                           28,874
<TOTAL-COSTS>                                   85,475
<OTHER-EXPENSES>                                 4,472<F1>
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                                   0
<INCOME-PRETAX>                                 27,981
<INCOME-TAX>                                    11,690
<INCOME-CONTINUING>                             16,826
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    16,826
<EPS-PRIMARY>                                     0.41
<EPS-DILUTED>                                     0.40
<FN>
<F1>OTHER EXPENSES REFERS TO EXPENSES OF $2,600 INCURRED IN CONJUNCTION WITH 
THE ACQUISITION AND INTEGRATION OF INTRUSION DETECTION INC. AND OTHER EXPENSES 
OF $1,872 INCURRED IN CONNECTION WITH A THREATENED LITIGATION SETTLEMENT.
</FN>