<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED FINANCIAL STATEMENTS INCLUDED IN THE FORM 10-Q AND IS QUALIFIED IN
ITS ENTIRETY TO REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<RESTATED> 
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>                     <C>
<PERIOD-TYPE>                   6-MOS                   6-MOS                   12-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1998             DEC-31-1997
<PERIOD-START>                             JAN-01-1997             JAN-01-1998             JAN-01-1997
<PERIOD-END>                               JUN-30-1997             JUN-30-1998             DEC-31-1997
<CASH>                                          36,732                  11,587                  82,924
<SECURITIES>                                         0                  65,229                       0
<RECEIVABLES>                                   46,144                  77,803                  63,410
<ALLOWANCES>                                     1,132                   1,203                   1,215
<INVENTORY>                                          0                       0                       0
<CURRENT-ASSETS>                                87,243                 161,236                 151,362
<PP&E>                                           8,374                  16,966                  11,263
<DEPRECIATION>                                   2,119                   3,906                   2,488
<TOTAL-ASSETS>                                  93,498                 176,142                 162,060
<CURRENT-LIABILITIES>                           35,292                  41,076                  40,434
<BONDS>                                              0                       0                       0
<PREFERRED-MANDATORY>                                0                       0                       0
<PREFERRED>                                          0                       0                       0
<COMMON>                                           233                     490                     252
<OTHER-SE>                                      55,444                 133,083                 119,174
<TOTAL-LIABILITY-AND-EQUITY>                    93,498                 176,142                 162,060
<SALES>                                        104,244                 174,170                 240,448
<TOTAL-REVENUES>                               104,244                 174,170                 240,448
<CGS>                                           74,386                 117,122                 167,685
<TOTAL-COSTS>                                   94,795                 150,370                 214,343
<OTHER-EXPENSES>                                   258                     258                     518
<LOSS-PROVISION>                                   312                     333                   1,000
<INTEREST-EXPENSE>                               (767)                 (1,403)                 (1,193)
<INCOME-PRETAX>                                 10,216                  21,991                  27,298
<INCOME-TAX>                                     4,206                   9,294                  11,231
<INCOME-CONTINUING>                              6,010                  12,697                  16,067
<DISCONTINUED>                                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0
<CHANGES>                                            0                       0                       0
<NET-INCOME>                                     6,010                  12,697                  16,067
<EPS-PRIMARY>                                     0.13                    0.26                    0.35
<EPS-DILUTED>                                     0.13                    0.26                    0.35
        

</TABLE>