FIRST AMENDMENT TO 1997 SECURITY AGREEMENT This First Amendment to 1997 Security Agreement is made as of May 15, 1998 to the 1997 Security Agreement (the "Agreement") dated as of February 26, 1997, among Data Transmission Network Corporation, First...

                   FIRST AMENDMENT TO 1997 SECURITY AGREEMENT


     This First Amendment to 1997 Security  Agreement is made as of May 15, 1998
to the 1997 Security  Agreement (the "Agreement") dated as of February 26, 1997,
among Data Transmission Network Corporation, First National Bank of Omaha, First
National Bank,  Wahoo,  Nebraska,  NBD Bank,  Norwest Bank Nebraska,  N.A., U.S.
Bank, National Association (formerly known as First Bank, National Association),
The Sumitomo Bank, Ltd.,  Mercantile Bank of St. Louis,  N.A., Bank of Montreal,
LaSalle National Bank, and  Nationsbank,  N.A.  ("Nationsbank,"  as successor in
interest to The Boatmen's National Bank of St. Louis).

     The  parties  hereto  acknowledge  and  agree  that all  references  in the
Agreement to The  Boatmen's  National Bank of St. Louis shall be deemed to refer
to  Nationsbank  and that First National Bank of Omaha shall hold the Collateral
described in the  Agreement on behalf of the lenders named therein and on behalf
of  Nationsbank  as a new  Revolving  Lender  under  the 1997  Revolving  Credit
Agreement  dated as of February  26,  1997,  as amended from time to time by the
parties thereto.


                               DATA TRANSMISSION NETWORK CORPORATION



                               By /s/ Xxxxx X. Xxxxxx
                               Its: VP, CFO and Secretary



                               FIRST NATIONAL BANK OF OMAHA, as agent for itself
                               and the other banks party to the Agreement


                               By /s/ Xxxxx X. Xxxxxx
                               Its: Vice President

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