stream ciphers encrypt the data bit by bit. In this research a new model of stream cipher SNOW 2.0 has been proposed i.e. Non linear modified SNOW 2.0 using one Linear Feedback Shift Register (LFSR) with the embedding of non linear function in the model. The analysis of Guess and Determined (GD) attack has been done to check its security with respect to previous versions. The proposed model contains one Linear Feedback Shift Register (LFSR) along with the non linear function which increases the strength of the stream cipher, to make the static nature of modified SNOW 2.0 dynamic. The Experimental analysis show that such a mechanism has been built which provides more security than the previous version of modified SNOW 2.0 in which non linearity was either not introduced or it was introduced using two Linear Feedback Shift Registers (LFSRs). It is concluded that this version is more powerful with respect to the security of plain text against Guess and Determined attack (GD) as compared to the previous versions.