5

THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE AUDITED FINANCIAL STATEMENTS OF NETWORK-1 SECURITY SOLUTIONS, INC. FOR THE PERIOD ENDED DECEMBER 31, 1999 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.

12-MOS DEC-31-1999 JAN-01-1999 DEC-31-1999 3,023,000 0 105,000 40,000 2,000 3,331,000 506,000 81,000 4,596,000 924,000 0 0 5,000 50,000 2,114,000 4,596,000 260,000 394,000 95,000 1,081,000 6,006,000 10,000 0 (6,561,000) 0 (6,561,000) (385,000) 0 0 (6,946,000) (1.92) (1.92)