<PAGE>   1
 
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                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
 
                                  FORM 10-K/A
 
<TABLE>
<S>     <C>
[X]         ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                      SECURITIES EXCHANGE ACT OF 1934

                FOR THE FISCAL YEAR ENDED DECEMBER 31, 1998

                                     OR

[ ]       TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                      SECURITIES EXCHANGE ACT OF 1934
</TABLE>
 
             FOR THE TRANSITION PERIOD FROM           TO
 
                       COMMISSION FILE NUMBER: 000-24931
 
                    SECURITY FIRST TECHNOLOGIES CORPORATION
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
 
<TABLE>
<S>                                            <C>
                   DELAWARE                                      58-2395199
       (State or other jurisdiction of                        (I.R.S. Employer
        incorporation or organization)                      Identification No.)

     3390 PEACHTREE ROAD, NE, SUITE 1700
               ATLANTA, GEORGIA                                    30326
   (Address of principal executive offices)                      (Zip Code)
</TABLE>
 
       REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (404) 812-6200
 
          SECURITIES REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT:
                                 Not Applicable
 
          SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT:
 
                    Common Stock, par value $0.01 per share
                                 Title of Class
 
     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports) and (2) has been subject to such
filing requirements for the past 90 days.  Yes X.     No____.
 
     Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K.  [ ]
 
     As of March 24, 1999, the aggregate market value of the shares of common
stock of the registrant issued and outstanding on such date, excluding 2,084,011
shares held by all affiliates of the registrant, was approximately $642,391,000.
This figure is based on the closing sales price of $62.50 per share of the
registrant's common stock on March 24, 1999, and excludes shares held by
directors and executive officers because such persons may be deemed to be
affiliates. This reference to affiliate status is not necessarily a conclusive
determination for other purposes.
 
     Shares of common stock outstanding as of March 24, 1999: 12,362,267
 
                      DOCUMENTS INCORPORATED BY REFERENCE
 
     List hereunder the following documents if incorporated by reference and the
Part of the Form 10-K into which the document is incorporated:
 
     Not applicable.
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<PAGE>   2
 
ITEM 10.  DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT.
 
INFORMATION AS TO DIRECTORS AND EXECUTIVE OFFICERS
 
     The following table sets forth the names of our current directors and
executive officers. Also provided is information as to each person's age at
December 31, 1998, the periods during which he has served as a director of S1
and its predecessor, Security First Network Bank, and positions currently held
with S1.
 
<TABLE>
<CAPTION>
                                   AGE AT
                                DECEMBER 31,   DIRECTOR   EXPIRATION
NAME                                1998        SINCE      OF TERM          POSITIONS HELD WITH S1
----                            ------------   --------   ----------        ----------------------
<S>                             <C>            <C>        <C>          <C>
Robert W. Copelan, D.V.M......       72          1995        1999      Director
Dorsey R. Gardner.............       56          1998        2001      Director
James S. Mahan, III...........       47          1995        2000      Chairman, Chief Executive Officer
                                                                         and President
Joseph S. McCall..............       49          1998        2001      Director
Howard J. Runnion, Jr.........       69          1995        2000      Director
Robert F. Stockwell...........       44            --          --      Chief Financial Officer and
                                                                         Treasurer
Daniel H. Drechsel............       38            --          --      President and Chief Operating
                                                                         Officer of S1's operating
                                                                         subsidiary
</TABLE>
 
     The following information concerns the principal occupation of each of our
directors and executive officers for the past five years. The executive officers
are elected by the board to serve a one-year term.
 
     Robert W. Copelan, D.V.M. has been President of Copelan & Thornbury, Inc.
in Paris, Kentucky since 1959 and President of R.W. Copelan, PSC in Paris,
Kentucky since 1979. Dr. Copelan is a veterinarian in private practice. From
1987 through September 1996, Dr. Copelan served on the board of directors of
Cardinal Bancshares, Inc. and some of its subsidiaries. He served on the board
of Security First Network Bank from 1995 until its sale in 1998. He has served
as a director of S1 since May 1998. Dr. Copelan is the stepfather of James S.
Mahan, III, S1's Chairman, President and Chief Executive Officer.
 
     Dorsey R. Gardner has served as a director of S1 since his appointment in
June 1998. Mr. Gardner has served as general partner of Hollybank Investments,
LP from 1993 to the present. Since 1980, he has served as President of Kelso
Management Co., Inc., advisor to Fidelity International Limited, Integrity
Fund-FM&R private capital, American Values I-IV, Fidelity American Situations
Trust, Fidelity Discovery Fund, Johnson family accounts, Johnson Foundation, and
Fidelity Foundation from 1980 to 1993 and adviser to Hollybank Investments, LP
from 1993 to the present. Mr. Gardner has served on the board of directors of
several corporations, and is currently a member of the boards of Crane Company
and Filene's Basement.
 
     James S. Mahan, III served as the Chief Executive Officer and a director of
Security First Network Bank from 1995 until its sale in 1998. He has served as a
director of S1 since May 1998, as Chief Executive Officer and President since
June 1998 and as Chairman of the Board since February 1999. He also has served
as Chairman of the Board of S1's operating subsidiary since May 1996. Mr. Mahan
was the Chairman of the Board and Chief Executive Officer of Cardinal
Bancshares, Inc., as well as some of its subsidiaries from November 1987 until
September 1996. Mr. Mahan is the stepson of director Robert W. Copelan.
 
     Joseph S. McCall has served as a director of S1 since his appointment in
October 1998. In 1986, Mr. McCall founded and remains the President of McCall
Consulting Group, a company that provides consulting primarily to software
companies that are building software products with new technology or
transitioning old products to new technology. McCall Consulting also provides
direct sales and training support to enabling technology software companies that
are launching products with leading edge technologies. Since 1991, Mr. McCall
has also served as a director of Clarus Corp. (formerly known as SQL Financials
International, Inc.), a publicly traded software company that sells web-enabled
financial and human resource application software. Mr. McCall founded SQL in
1991 and served as Chief Executive Officer until early 1998. In 1994, Mr. McCall
founded Technology Ventures, LLC, which is an investment
                                        1
<PAGE>   3
 
company that owns all of McCall Consulting and is the largest single shareholder
of Clarus Corp. Technology Ventures serves as Mr. McCall's vehicle for investing
in new companies and providing equity incentives to employees of the companies
in which Technology Ventures has invested. Mr. McCall currently is a member of
the boards of directors of McCall Consulting and Technology Ventures.
 
     Howard J. Runnion, Jr. was Vice Chairman of the Board and Chief Financial
Officer of The Wachovia Corporation in Winston-Salem, North Carolina from
December 1985 to June 1990. Since 1992, Mr. Runnion has served as a consultant
and an insurance broker. Mr. Runnion was a director of Cardinal Bancshares, Inc.
and some of its subsidiaries until September 1996 and a director of Security
First Network Bank from 1995 until its sale in 1998. He has served as a director
of S1 since May 1998.
 
     Robert F. Stockwell served as the Treasurer and Chief Financial Officer of
Security First Network Bank from 1995 until its sale in 1998, and has served as
Treasurer and Chief Financial Officer of S1's operating subsidiary since May
1996. He has served as Chief Financial Officer and Treasurer of S1 since June
1998. From June 1998 to November 1998, he also served as Secretary of S1. From
October 1996 through September 1998, he served as Acting President of Security
First Network Bank. Mr. Stockwell served as Treasurer of Cardinal Bancshares,
Inc. from January 1994 to September 1996 and as a director of Jefferson Banking
Company during 1994. From 1987 to 1993, Mr. Stockwell was Executive Vice
President and Chief Financial Officer of Security Financial Holding Company, a
thrift holding company located in Durham, North Carolina.
 
     Daniel H. Drechsel has served as President and Chief Operating Officer of
Security First Technologies, Inc., S1's operating subsidiary, since June 1998.
In his position as our Chief Operating Officer, Mr. Drechsel oversees the
day-to-day operations of S1's operating subsidiary. Prior to joining our
operating subsidiary, Mr. Drechsel served as Vice President of Marketing with
Meta4 Software, S.A., a Madrid-based enterprise software company from September
1997 to June 1998. Mr. Drechsel served as General Manager of ECPartners, a joint
venture between Checkfree Corporation and Automatic Data Processing, Inc.'s
Electronic Services Division from 1995 to 1997. Mr. Drechsel served on the board
of directors of InfoWave Technologies, Inc. from 1997 to 1999. Mr. Drechsel's
previous experience included a variety of management positions in sales,
marketing and software development at both Automatic Data Processing and Dun &
Bradstreet Corporation.
 
SECTION 16(A) BENEFICIAL OWNERSHIP REPORTING COMPLIANCE
 
     Section 16(a) of the Securities Exchange Act of 1934 requires our directors
and officers, and persons who own more than 10% of our common stock, to file
with the Securities and Exchange Commission initial reports of ownership of our
equity securities and to file subsequent reports when there are changes in their
ownership. Based on a review of reports submitted to us, we believe that during
the fiscal year ended December 31, 1998, all Section 16(a) filing requirements
applicable to our directors, officers and more than 10% owners were complied
with on a timely basis, other than a Form 4 that was not timely filed by Mr.
Stockwell for one transaction which was reflected in a Form 5 filing.
 
ITEM 11.  EXECUTIVE COMPENSATION.
 
EXECUTIVE AND DIRECTOR COMPENSATION
 
     The following table shows the cash compensation paid by S1 for the last
three fiscal years, as well as compensation paid or accrued for those years, to
the Chief Executive Officer and the one other highest paid executive officer
serving at December 31, 1998, whose total annual salary and bonus for the fiscal
year ended December 31, 1998 exceeded $100,000. We refer to these two officers
as our named executive officers. No stock appreciation rights have been granted
by S1 or its predecessor, Security First Network Bank.
 
                                        2
<PAGE>   4
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                                                       LONG-TERM
                                                                                     COMPENSATION
                                                                                     -------------
                                                                                        AWARDS
                                                   ANNUAL COMPENSATION               -------------
                                       -------------------------------------------    SECURITIES
NAME AND                                                           OTHER ANNUAL       UNDERLYING         ALL OTHER
PRINCIPAL POSITION              YEAR   SALARY($)      BONUS($)  COMPENSATION($)(B)   OPTIONS($)(C)   COMPENSATION($)(D)
------------------              ----   ---------      --------  ------------------   -------------   ------------------
<S>                             <C>    <C>            <C>       <C>                  <C>             <C>
James S. Mahan, III...........  1998   $200,000             --       $    --                 --            $7,872
  Chairman, Chief Executive     1997    200,000             --         9,861                 --             9,756
  Officer and President         1996     87,535(a)          --        68,080                 --             3,131
Robert F. Stockwell...........  1998   $150,000             --       $    --            100,000            $5,950
  Chief Financial Officer       1997    119,141             --            --             40,000             6,392
  and Treasurer                 1996    104,962             --        70,009                 --             2,272
</TABLE>
 
---------------
 
 (a) During the first nine months of 1996, Mr. Mahan's annual rate of salary was
     $50,000. During that time, he also served as the Chairman and Chief
     Executive Officer of Cardinal Bancshares, Inc., which was then the parent
     of Security First Network Bank.
 
(b) For 1996, other annual compensation includes reimbursement of moving
    expenses of $56,880 for Mr. Mahan and $70,009 for Mr. Stockwell, including
    applicable taxes associated with these reimbursements.
 
 (c) Reflects the two-for-one split of our common stock paid on May 7, 1999.
 
(d) All other compensation includes contributions to S1's 401(k) plan and
    insurance premiums. 401(k) contributions for 1996, 1997 and 1998 were
    $2,501, $2,667 and $2,666 for Mr. Mahan; and $2,002, $3,292 and $2,750 for
    Mr. Stockwell. Insurance premiums for 1996, 1997 and 1998 were $630, $7,089
    and $5,206 for Mr. Mahan; and $270, $3,100 and $3,200 for Mr. Stockwell.
 
     Our directors do not receive any fees or other compensation for their
service as directors. Directors, however, are reimbursed for travel and other
expenses incurred in connection with attending meetings of our board of
directors. Upon joining the board of directors in 1998, Mr. Gardner and Mr.
McCall were awarded options to acquire 60,000 shares of our common stock under
our 1998 Directors' Stock Option Plan, as adjusted to reflect the two-for-one
split of our common stock paid on May 7, 1999.
 
EMPLOYMENT CONTRACTS
 
     We currently do not have any employment contracts or other compensatory
plans or arrangements relating to resignation, retirement or any other
termination of a named executive officers' employment with S1 or our operating
subsidiary or from a change in control of S1 or a change of the named executive
officer's responsibilities following a change in control of S1. Unvested stock
options, however, generally vest upon a change in control, as defined.
 
OPTION GRANTS
 
     The following table contains information concerning the grant of stock
options to the named executive officers during fiscal year 1998. The information
set forth in this table reflects the two-for-one split of our common stock paid
on May 7, 1999.
 
                                        3
<PAGE>   5
 
                       OPTION GRANTS IN LAST FISCAL YEAR
 
<TABLE>
<CAPTION>
                                                                  INDIVIDUAL GRANTS
                                 ------------------------------------------------------------------------------------
                                                                                                POTENTIAL REALIZABLE
                                                                                                        VALUE
                                                                                                  AT ASSUMED ANNUAL
                                                                                                        RATES
                                    NUMBER         % OF TOTAL                                      OF STOCK PRICE
                                 OF SECURITIES      OPTIONS                                         APPRECIATION
                                  UNDERLYING       GRANTED TO        EXERCISE                      FOR OPTION TERM
                                    OPTIONS        EMPLOYEES         OR BASE       EXPIRATION   ---------------------
NAME                              GRANTED(#)     IN FISCAL YEAR   PRICE($/SHARE)      DATE         5%          10%
----                             -------------   --------------   --------------   ----------   ---------   ---------
<S>                              <C>             <C>              <C>              <C>          <C>         <C>
Robert F. Stockwell............     100,000             5%           $3.3125         1/9/09     $208,321    $527,927
  Chief Financial Officer and
  Treasurer
</TABLE>
 
1998 OPTION EXERCISES AND VALUES
 
     The following table provides information on exercises of stock options
during fiscal year 1998 by the named executive officers and the value of
unexercised options at the end of the year. The information set forth in this
table reflects the two-for-one split of our common stock paid on May 7, 1999.
 
     AGGREGATED OPTION EXERCISES IN 1998 AND FISCAL YEAR-END OPTION VALUES
 
<TABLE>
<CAPTION>
                                                           NUMBER OF SECURITIES
                                                          UNDERLYING UNEXERCISED      VALUE OF UNEXERCISED IN-THE
                            SHARES                         OPTIONS AT FY-END(#)      MONEY OPTIONS AT FY-END($)(b)
                          ACQUIRED ON       VALUE        -------------------------   -----------------------------
NAME                      EXERCISE(#)   REALIZED($)(a)   EXERCISABLE/UNEXERCISABLE     EXERCISABLE/UNEXERCISABLE
----                      -----------   --------------   -------------------------   -----------------------------
<S>                       <C>           <C>              <C>                         <C>
James S. Mahan, III.....        --               --         1,393,800/464,600           $20,819,888/$6,939,963
Robert F. Stockwell.....    50,000         $253,125            69,380/176,460           $ 1,009,174/$2,254,301
</TABLE>
 
---------------
 
(a) Based on the market value of our common stock at date of exercise, less the
    exercise price.
 
(b) Based on the closing price per share of our common stock on December 31,
    1998 of $15.25 on the Nasdaq National Market, as adjusted to reflect the
    two-for-one split of our common stock paid on May 7, 1999, less the exercise
    price, of all unexercised stock options having an adjusted exercise price
    less than that market value.
 
COMPENSATION COMMITTEE REPORT ON EXECUTIVE COMPENSATION
 
     Since 1996 through the corporate reorganization of Security First Network
Bank in September 1998, the full board of directors of Security First Network
Bank served as a compensation committee. In the fourth quarter of 1998, a
separate compensation committee of the S1 board was established. The Chairman of
the compensation committee is Mr. McCall and the other members are Mr. Gardner
and Mr. Runnion. The compensation committee recommends to the full board of
directors, which has ultimate responsibility over compensation matters. Set
forth below is a report of the compensation committee addressing S1's
compensation policies for fiscal year 1998 as they affected our executive
officers.
 
     Compensation Policies for Executive Officers.  S1's executive compensation
policies are designed to provide competitive levels of compensation, to assist
S1 in attracting and retaining qualified executives and to encourage superior
performance. In determining levels of executive officers' overall compensation,
the qualifications and experience of the persons concerned, the size of the
company and the complexity of its operation, the financial condition, including
revenues, the compensation paid to other persons employed by the company and the
compensation paid to persons having similar duties and responsibilities in the
technology industry were considered. Compensation paid to our executive officers
in 1998 consisted of the following components: base salary, long-term incentives
(awards of stock options) and participation in S1's other employee benefit
plans. No bonuses were paid to executive officers for 1998. While each of these
components has a separate purpose and may have a different relative value to the
total, a significant portion of the total compensation package for 1998 for the
executive officers is highly dependent on the public market value of S1 and
total return to shareholders. Our executive officers have significant equity
interests in S1's success by virtue of stock based compensation.
 
                                        4
<PAGE>   6
 
     The compensation committee currently is re-evaluating S1's executive
compensation structure, and is likely to propose significant revisions. No
determination has been made regarding this matter and no date has been set for
making this determination.
 
     Base Salary.  Base salary is intended to signal the internal value of the
position. In establishing the 1998 salary for each executive officer, the
officer's responsibilities, qualifications and experience were considered. The
base salary for one of our executive officers increased in 1998 in recognition
of the responsibilities of that officer.
 
     Long-Term Incentive Compensation.  S1 uses stock options to provide
long-term incentive compensation. The compensation committee endorses the
position that stock ownership by management is beneficial in aligning
management's and shareholders' interests in the enhancement of shareholder
value. The purpose of stock option awards is to provide an opportunity for the
recipients to acquire or increase a proprietary interest in S1, thereby creating
a stronger incentive to expend maximum effort for the long-term growth and
success of S1 and encouraging recipients to remain in the employ of S1. Officers
and other full-time employees of S1 and its subsidiaries are eligible for grants
under our 1995 and 1997 stock option plans. Stock options are normally granted
each year with the size of the grants generally tied to and weighted
approximately equally based on an officer's responsibility level and
performance. During 1998, 400,000 stock options were granted to our executive
officers, as adjusted to reflect the two-for-one split of our common stock paid
on May 7, 1999.
 
     Other.  In addition to the compensation paid to executive officers
described above, executive officers received, along with and on the same terms
as other employees, certain benefits such as health insurance and participation
in S1's 401(k) Plan.
 
     CEO Compensation.  Since the company began its current internet business in
1995, the compensation for the Chief Executive Officer has been primarily cash
compensation in the form of a base salary, and stock-based in the form of
options. In 1998, the Chief Executive Officer's 1998 base salary was $200,000,
which was the same as his 1997 base salary. The Chief Executive Officer did not
receive a bonus or an award of stock options in 1997 or 1998. Nonetheless, as
noted above, a significant portion of S1's total compensation package is highly
dependent on the public market value of S1 and total return to shareholders.
This has been the case since the company began its operations as an internet
business in 1995. Notwithstanding that the Chief Executive Officer did not
receive an increase in base salary, a bonus or an award of stock options in
1998, the public market value of S1 common stock did increase significantly
during 1998, thereby considerably enhancing the value of long-term stock awards
granted to the Chief Executive Officer in previous years. At the beginning of
1998, the reported per share price of our common stock was $3.75, and at
year-end 1998 it was $15.25, in both cases, as adjusted for the two-for-one
split of our common stock paid on May 7, 1999. As noted above, the compensation
committee is re-evaluating the compensation structure for all the executive
officers, including the Chief Executive Officer.
 
     Internal Revenue Code Section 162(m).  In 1993, the Internal Revenue Code
of 1986, as amended, was amended to disallow publicly traded companies from
receiving a tax deduction on compensation paid to executive officers in excess
of $1 million (section 162(m) of the Code), unless, among other things, the
compensation meets the requirements for performance-based compensation. S1 has
not taken this limitation into account in the past in structuring most of its
equity compensation programs and in determining executive compensation. The
compensation committee expects to take the deductibility limit for compensation
into consideration when awarding equity-based compensation beginning in fiscal
1999.
 
                             Compensation Committee
                         ------------------------------
 
                               Dorsey R. Gardner
                          Joseph S. McCall (Chairman)
                             Howard J. Runnion, Jr.
 
PERFORMANCE OF OUR COMMON STOCK
 
     The following table sets forth comparative information regarding the
cumulative shareholder return on our common stock since May 26, 1996. Share
information from May 26, 1996 to September 30, 1998 is based
                                        5
<PAGE>   7
 
on the common stock of our predecessor, Security First Network Bank. Total
shareholder return is measured by dividing cumulative dividends for the
measurement period (assuming dividend reinvestment) plus share price change for
the period by the share price at the beginning of the measurement period.
Neither S1 nor Security First Network Bank has paid dividends on its common
stock from May 26, 1996 to December 31, 1998. Our cumulative shareholder return
over this period is based on an investment of $100 on May 26, 1996 and is
compared to the cumulative total return of the Interactive Week Internet Index
and the Nasdaq Composite Index.
 
                  COMPARISON OF CUMULATIVE TOTAL RETURN AMONG
         S1, INTERACTIVE WEEK INTERNET INDEX AND NASDAQ COMPOSITE INDEX
                     FROM MAY 26, 1996 TO DECEMBER 31, 1998
 
<TABLE>
<CAPTION>
                                                                    PERIOD ENDING
                                                            ------------------------------
COMPANY/INDEX NAME                                5/26/96   12/31/96   12/31/97   12/31/98
------------------                                -------   --------   --------   --------
<S>                                               <C>       <C>        <C>        <C>
Security First Technologies Corporation.........  $100.00   $ 25.00    $ 17.68    $ 74.39
Interactive Week Internet Index.................   100.00     92.89     100.10     238.53
Nasdaq Composite Index..........................   100.00    106.02     128.94     177.36
</TABLE>
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
     The Chairman of our compensation committee is Mr. McCall and the other
members of the committee are Mr. Gardner and Mr. Runnion. None of the members of
this committee have served as an officer or employee of S1 or its operating
subsidiary. During 1998, S1 used technology consulting services from McCall
Consulting Group. Mr. McCall is the president of McCall Consulting. During 1998,
the total amount paid to McCall Consulting was $1.1 million. At December 31,
1998, S1 had outstanding payables to McCall Consulting Group of $282,000.
 
ITEM 12.  SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT.
 
STOCK OWNED BY DIRECTORS AND MANAGEMENT
 
     The following table sets forth information known to us regarding the
beneficial ownership of our common stock as of April 21, 1999 by each of our
directors and the named executive officers and by all of our directors and
executive officers as a group. At April 21, 1999, there were 25,172,160 shares
of our common stock outstanding, as adjusted to reflect the two-for-one split of
our common stock paid on May 7, 1999. Information for Mr. Michael C. McChesney,
who resigned as Chairman of the Board of S1 in February 1999, is not included in
this table and is set forth in the table under the caption "Principal
Shareholders." All information as to beneficial ownership has been provided to
us by the directors and executive officers, and unless otherwise indicated, each
of the directors and executive officers has sole voting and investment power
over all of shares that they beneficially own. The information set forth in this
table reflects the two-for-one split of our common stock paid on May 7, 1999.
 
<TABLE>
<CAPTION>
                                                                 NUMBER OF SHARES        PERCENT OF
                                                                   AND NATURE OF        COMMON STOCK
NAME AND POSITION(S) WITH S1                                  BENEFICIAL OWNERSHIP(a)   OUTSTANDING
----------------------------                                  -----------------------   ------------
<S>                                                           <C>                       <C>
James S. Mahan, III.........................................         2,019,442(b)           7.47%
  Chairman, Chief Executive Officer and President
Robert F. Stockwell.........................................           243,388(c)              *
  Chief Financial Officer and Treasurer
Daniel H. Drechsel..........................................                80(d)              *
  President and Chief Operating Officer of
  S1's operating subsidiary
</TABLE>
 
                                        6
<PAGE>   8
 
<TABLE>
<CAPTION>
                                                                 NUMBER OF SHARES        PERCENT OF
                                                                   AND NATURE OF        COMMON STOCK
NAME AND POSITION(S) WITH S1                                  BENEFICIAL OWNERSHIP(a)   OUTSTANDING
----------------------------                                  -----------------------   ------------
<S>                                                           <C>                       <C>
Robert W. Copelan, D.V.M....................................           287,064(e)           1.13%
  Director
Dorsey R. Gardner...........................................         1,370,200(f)           5.44%
  Director
Joseph S. McCall............................................            27,000(g)              *
  Director
Howard J. Runnion, Jr.......................................           220,848(h)              *
  Director
All directors and executive officers of S1
  as a group (7 persons)....................................         4,168,022             15.22%
</TABLE>
 
---------------
 
*   Less than one percent.
 
(a) In accordance with Rule 13d-3 under the Securities Exchange Act of 1934, a
    person is deemed to be the beneficial owner, for purposes of this table, of
    any shares of common stock if that person has or shares voting power or
    investment power over the security, or has the right to acquire beneficial
    ownership at any time within 60 days from April 21, 1999. For this table,
    voting power includes the power to vote or direct the voting of shares and
    investment power includes the power to dispose or direct the disposition of
    shares.
 
(b) The share ownership of Mr. Mahan includes 1,858,400 shares of common stock
    that would be issued upon the exercise of options exercisable within 60 days
    of April 21, 1999, 1,224 shares that are held directly by Mr. Mahan, 9,570
    shares held in S1's 401(k) plan and 150,248 shares held by his wife.
 
(c) The share ownership of Mr. Stockwell includes 140,840 shares of common stock
    that would be issued upon the exercise of options exercisable within 60 days
    of April 21, 1999, 90,576 shares held jointly with his wife, 6,410 shares
    held in S1's 401(k) plan, 3,728 shares held in an IRA and 1,834 shares held
    by his mother in an IRA.
 
(d) The share ownership of Mr. Drechsel includes 80 shares held in S1's 401(k)
    plan.
 
(e) The share ownership of Dr. Copelan includes 185,840 shares of common stock
    that would be issued upon the exercise of options exercisable within 60 days
    of April 21, 1999, 83,872 shares that are held directly by Dr. Copelan,
    14,904 shares that are held by the Robert W. Copelan D.V.M. Retirement Plan
    and 2,448 shares that are held by his wife.
 
(f) The share ownership of Mr. Gardner includes 153,000 shares held directly by
    Mr. Gardner and 1,217,200 shares held by Hollybank Investments, LP, a
    limited partnership of which Mr. Gardner is the general partner.
 
(g) The share ownership of Mr. McCall includes 25,000 shares held directly by
    Mr. McCall and 2,000 shares held by Mr. McCall in an IRA.
 
(h) The share ownership of Mr. Runnion includes 20,848 shares of common stock
    that would be issued upon the exercise of options exercisable within 60 days
    of April 21, 1999 and 200,000 shares owned directly by Mr. Runnion.
 
                                        7
<PAGE>   9
 
PRINCIPAL SHAREHOLDERS
 
     The following table sets forth information known to us regarding beneficial
ownership of our common stock as of April 21, 1999 by each person believed by
management to be the beneficial owner of more than 5% of our outstanding common
stock. The information set forth in this table reflects the two-for-one split of
our common stock paid on May 7, 1999.
 
<TABLE>
<CAPTION>
                                                        NUMBER OF SHARES        PERCENT OF
                                                          AND NATURE OF        COMMON STOCK
NAME AND ADDRESS OF BENEFICIAL OWNER                 BENEFICIAL OWNERSHIP(a)   OUTSTANDING
------------------------------------                 -----------------------   ------------
<S>                                                  <C>                       <C>
Michael C. McChesney...............................       2,384,032(b)            9.13%
  37 Muscogee Avenue
  Atlanta, GA 30305
Lord, Abbett & Co..................................       2,037,390(c)            8.09%
  767 Fifth Avenue
  New York, NY 10153
James S. Mahan, III................................       2,019,442(d)            7.47%
  3390 Peachtree Road, NE
  Atlanta, GA 30326
Dorsey R. Gardner..................................       1,370,200(e)            5.44%
  One International Place
  Suite 2401
  Boston, MA 02110
</TABLE>
 
---------------
 
(a) In accordance with Rule 13d-3 under the Securities Exchange Act of 1934, a
    person is deemed to be the beneficial owner, for purposes of this table, of
    any shares of common stock if that person has or shares voting power or
    investment power over the security, or has the right to acquire beneficial
    ownership at any time within 60 days from April 21, 1999. For this table,
    voting power includes the power to vote or direct the voting of shares and
    investment power includes the power to dispose or direct the disposition of
    shares.
 
(b) The share ownership of Mr. McChesney includes 928,800 shares issuable upon
    the exercise of options that are exercisable within 60 days of April 21,
    1999, 1,438,692 shares owned directly by Mr. McChesney, 1,180 shares held in
    S1's 401(k) plan and 15,360 shares held by two members of his family. Mr.
    McChesney served as Chairman of the Board of S1 until his resignation in
    February 1999.
 
(c) Lord, Abbett & Co. filed a Schedule 13G with the Securities and Exchange
    Commission dated February 12, 1999 reporting sole voting and dispositive
    power over the shares listed above.
 
(d) The share ownership of Mr. Mahan includes 1,858,400 shares of common stock
    that would be issued upon the exercise of options exercisable within 60 days
    of April 21, 1999, 1,224 shares that are held directly by Mr. Mahan, 9,570
    shares held in S1's 401(k) plan and 150,248 shares held by his wife.
 
(e) The share ownership of Mr. Gardner includes 153,000 shares held directly by
    Mr. Gardner and 1,217,200 shares held by Hollybank Investments, LP, a
    limited partnership of which Mr. Gardner is the general partner.
 
ITEM 13.  CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS.
 
     Prior to our 1998 sale of Security First Network Bank, the bank made loans
to its directors and executive officers for the financing of their homes, as
well as home improvement and consumer loans. It is the belief of management that
these loans were made in the ordinary course of business, were made on
substantially the same terms, including interest rates and collateral, as those
prevailing at the time for comparable transactions with other persons, and
neither involved more than normal risk of collectability nor presented other
unfavorable features.
 
                                        8
<PAGE>   10
 
     During the latter part of 1996, among its ordinary course research and
development activities, the company that is now S1's operating subsidiary
started a project known as "Webtone." The Webtone project was established to
assess the customer care issues raised as a result of interacting with retail
customers over new delivery channels and subsequently to develop software
solutions to resolve these issues more efficiently. In November 1997, after the
assessment phase of the project was completed at a cost of approximately
$300,000, the board of directors determined not to proceed with Webtone,
primarily because of the board's uncertainty about the potential profitability
of the project and because of the limited resources, both capital and personnel,
of the operating subsidiary. The board believes this decision is consistent with
the determination to discontinue the banking business of Security First Network
Bank and focus resources on the Virtual Financial Manager suite of products and
related services. With the board's full knowledge and agreement, Michael C.
McChesney created and funded his own company to develop Webtone. Mr. McChesney
resigned as the Chairman of the Board of S1 in February 1999. In undertaking
these activities, Mr. McChesney and the board of directors have acknowledged
that Webtone and Mr. McChesney should enter into some form of arrangement for a
future business relationship. However, the parties have not determined what that
arrangement should be. Since abandoning the Webtone project, S1's operating
subsidiary has provided Webtone with administrative and technical services on a
time and materials basis amounting to approximately $192,000 in 1998 and $80,000
in 1997. As of December 31, 1998, the operating subsidiary had a receivable from
Webtone related to these services of $173,000.
 
     During 1998, S1 used technology consulting services from McCall Consulting
Group. The president of McCall Consulting, Mr. Joseph S. McCall, is one of our
directors. During 1998, the total amount paid to McCall Consulting was
approximately $1.1 million. At December 31, 1998 S1 had outstanding payables to
McCall Consulting of $282,000.
 
                                        9
<PAGE>   11
 
                                   SIGNATURES
 
     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized, as of May 13, 1999.
 
                                          SECURITY FIRST TECHNOLOGIES
                                          CORPORATION
 
                                          By:    /s/ ROBERT F. STOCKWELL
                                            ------------------------------------
                                            Robert F. Stockwell
                                            Chief Financial Officer and
                                              Treasurer
 
                                       10