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                                                                    EXHIBIT 99.1

                    CERTIFICATION PURSUANT TO SECTION 906 OF
                         THE SARBANES-OXLEY ACT OF 2002

    In connection with the Quarterly Report of NetScout Systems, Inc. (the
"Company") on Form 10-Q for the quarterly period ended September 30, 2002, as
filed with the Securities and Exchange Commission on the date hereof (the
"Report"), I, Anil K. Singhal, Chief Executive Officer of the Company, hereby
certify pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906
of the Sarbanes-Oxley Act of 2002, that: (1) the Report fully complies with the
requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934;
and (2) the information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of the Company.

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Date: November 8, 2002                         By:                 /s/ ANIL K. SINGHAL
                                                    ------------------------------------------------
                                                                     Anil K. Singhal
                                                                 CHIEF EXECUTIVE OFFICER
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