THIRD AMENDMENT TO 1996 RESTATED SECURITY AGREEMENT


         THIS THIRD  AMENDMENT TO 1996 RESTATED  SECURITY  AGREEMENT (the "Third
Amendment") is intended to amend the 1996 RESTATED  SECURITY  AGREEMENT dated as
of May 3, 1996, as previously  amended (the  "Security  Agreement") by the FIRST
AMENDMENT TO 1996 RESTATED SECURITY  AGREEMENT (the "First  Amendment") dated as
of June 28, 1996 and the SECOND  AMENDMENT TO 1996 RESTATED  SECURITY  AGREEMENT
(the  "Second  Amendment")  dated  as of  July  31,  1996,  by  and  among  DATA
TRANSMISSION  NETWORK  CORPORATION,  a Delaware corporation having its principal
place of business at Suite 200, 9110 West Dodge Road, Omaha, Nebraska 68114 (the
"Debtor"),  FIRST NATIONAL BANK OF OMAHA, a national banking  association having
its principal place of business at One First National  Center,  Omaha,  Nebraska
68102 as agent  ("Secured  Party") for itself and FIRST  NATIONAL  BANK,  WAHOO,
NEBRASKA,  a national banking association having its principal place of business
at Wahoo, Nebraska 68066 ("FNB-W"), NBD BANK, a bank organized under the laws of
the State of Michigan  having its  principal  place of business at 611  Woodward
Avenue, Detroit, Michigan 48226 ("NBD"), NORWEST BANK NEBRASKA, N.A., a national
banking  association  having its principal  place of business at 20th and Farnam
Streets, Omaha, Nebraska 68102 ("Norwest"),  FIRST BANK, NATIONAL ASSOCIATION, a
national banking  association having its principal place of business at 13th and
M Streets,  Lincoln,  Nebraska 68508 ("First Bank") (it being  acknowledged that
First Bank is the successor in interest to FirsTier Bank, National  Association,
Lincoln,  Nebraska  ("FirsTier")),  THE BOATMEN'S  NATIONAL BANK OF ST. LOUIS, a
national  banking  association  having its  principal  place of  business at One
Boatmen's Plaza, 800 Market Street, P.O. Box 236, St. Louis, Missouri 63166-0236
("Boatmen's"),  THE SUMITOMO BANK, LIMITED, a Japanese bank being represented by
its office at 200 North  Broadway,  Suite 1625,  St. Louis,  Missouri  63102 and
acting through its Chicago branch  ("Sumitomo"),  MERCANTILE  BANK OF ST. LOUIS,
N.A., a national banking  association  having its principal place of business at
One Mercantile Center,  7th and Washington  Streets,  St. Louis,  Missouri 63101
("Mercantile"),  and LASALLE NATIONAL BANK, a national banking association being
represented by its office at One Metropolitan  Square,  211 North Broadway,  St.
Louis,  Missouri 63102  ("LaSalle")  (collectively,  and together with any other
Lender that  hereinafter  becomes a party to any "Loan Agreement" as hereinafter
defined,  the  "Lenders").  (In accordance  with the Third Amendment to the 1996
Revolving  Credit  Agreement,  as  described  in Section  3(ii) of the  Security
Agreement, Ag America is no longer a Lender.)



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         1.       The following sentence shall be added to the end of Section 1
                  of the Security Agreement:

                           All  capitalized  terms not defined in this  Security
                           Agreement shall have their respective meanings as set
                           forth in the Revolving Credit Agreement, as described
                           in Section 3(ii) below.
         2.       The following  shall  be  added  to the end of clause (iv) of
                  Section 3 of the Security Agreement:

                           or under  any  interest  rate  protection   agreement
                           entered into by Debtor with one or more Lenders;

         3.       Clause (v) of Section  3 of  the  Security Agreement shall be
                  amended to read as follows:

                           (v)  under  any  and  all  Notes  previously,  now or
                           hereafter  made by Debtor to the Lenders  pursuant to
                           any of the  foregoing  Loan  Agreements  and interest
                           rate protection agreements (all of which are referred
                           to herein as the "Related  Loan  Agreements")  or any
                           predecessor  loan  agreements,   including,   without
                           limitations,  the  Existing  Term Notes and any notes
                           given in extension,  renewal or  substitution  of the
                           Notes;

         4.       The last sentence of Section  9(i)  of the Security  Agreement
                  shall be amended to read as follows:

                           Any amounts or payments  obtained upon disposition of
                           any property  securing an  obligation  of Debtor to a
                           Lender shall be applied as provided in Article VII of
                           the 1996 Revolving  Credit  Agreement as in effect on
                           December 27, 1996.

         5. Debtor hereby  restates,  as of the date hereof,  for the benefit of
the Lenders the  representations  and  warranties  set forth in Section 4 of the
Agreement.  Notwithstanding  the  foregoing,  representations  of  Debtor  as to
filings in  respect  of the  Collateral  are  hereby  amended  to  reflect  such
additional filings as shall have been made in favor of the Lenders.

         6. This Third  Amendment  shall be  effective  as of December 27, 1996.
References in the Notes,  the Related Loan  Agreements and similar  documents to
the "Security  Agreement" or the "1996 Restated  Security  Agreement" shall mean
the Security Agreement, as amended by the First Amendment,  the Second Amendment
and this Third Amendment.



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         IN WITNESS WHEREOF,  the undersigned have executed this THIRD AMENDMENT
TO 1996 RESTATED SECURITY AGREEMENT as of December 27, 1996.


                                                     DATA TRANSMISSION NETWORK
                                                     CORPORATION


                                                     By
                                                     Title





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                                                    FIRST NATIONAL BANK OF OMAHA


                                                     By
                                                     Title


 3797

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