<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
       
<S>                             <C>                     <C>                     <C>                     <C>
<PERIOD-TYPE>                   6-MOS                   9-MOS                   12-MOS                   3-MOS
<FISCAL-YEAR-END>                          SEP-30-1997             SEP-30-1997             SEP-30-1997             SEP-30-1998
<PERIOD-START>                             OCT-01-1996             OCT-01-1996             OCT-01-1997             OCT-01-1997
<PERIOD-END>                               MAR-31-1997             JUN-30-1997             SEP-30-1997             DEC-31-1997
<CASH>                                           4,971                   5,685                   9,998                  37,159
<SECURITIES>                                    26,308                  25,458                  25,739                       0
<RECEIVABLES>                                    4,555                   5,861                   6,830                   7,087
<ALLOWANCES>                                       369                     447                     245                     581 
<INVENTORY>                                        164                     181                     167                      94 
<CURRENT-ASSETS>                                36,194                  37,515                  43,582                  44,767 
<PP&E>                                           4,798                   5,714                   6,655                   7,231 
<DEPRECIATION>                                   1,680                   2,149                   2,489                   2,775 
<TOTAL-ASSETS>                                  41,482                  43,321                  50,079                  51,993 
<CURRENT-LIABILITIES>                            9,134                   9,981                   9,808                  10,114 
<BONDS>                                              0                       0                     351                       0 
<PREFERRED-MANDATORY>                                0                       0                       0                       0 
<PREFERRED>                                          0                       0                       0                       0 
<COMMON>                                             8                       8                       8                       8 
<OTHER-SE>                                      31,912                  32,963                  39,912                  41,558 
<TOTAL-LIABILITY-AND-EQUITY>                    41,482                  43,321                  50,079                  51,993 
<SALES>                                         13,966                  23,127                  33,409                  10,858 
<TOTAL-REVENUES>                                13,966                  23,127                  33,409                  10,858 
<CGS>                                            2,058                   3,507                   4,937                   1,472 
<TOTAL-COSTS>                                    2,058                   3,507                   4,937                   1,472 
<OTHER-EXPENSES>                                11,265                  18,031                  25,335                   7,804 
<LOSS-PROVISION>                                    85                      78                     241                       0 
<INTEREST-EXPENSE>                                  24                      31                       0                      11 
<INCOME-PRETAX>                                  1,103                   2,527                   4,293                   2,178 
<INCOME-TAX>                                       456                     883                   1,459                     621 
<INCOME-CONTINUING>                                647                   1,644                   2,834                   1,557 
<DISCONTINUED>                                       0                       0                       0                       0 
<EXTRAORDINARY>                                      0                       0                       0                       0 
<CHANGES>                                            0                       0                       0                       0 
<NET-INCOME>                                       647                   1,644                   2,834                   1,557 
<EPS-PRIMARY>                                     0.09                    0.22                    0.32                    0.16
<EPS-DILUTED>                                     0.07                    0.16                    0.27                    0.14
                                               

</TABLE>