6. A computer-implemented method comprising: determining, by an anti-spam module, an approximate display location of one or more embedded images within an electronic mail (email) message; identifying, by the anti-spam module, existence of one or more abnormal factors associated with the one or more embedded images; quantifying, by the anti-spam module, a number of text strings that are included in the embedded image by analyzing one or more blocks of the binarized representation with a text string measurement algorithm; classifying, by the anti-spam module, the email message as spam or clean based on the approximate display location, the existence of one or more abnormal factors and the number of text strings; wherein the anti-spam module is implemented in one or more processors and one or more non-transitory computer-readable storage media of one or more computer systems, the one or more non-transitory computer-readable storage media having instructions tangibly embodied therein representing the anti-spam module that are executable by the one or more processors; and wherein the one or more blocks comprise M×N virtual blocks and wherein the text string measurement algorithm employs equations having a general form as follows: T = ∑ m = 0 M ⁢ ∑ n = 0 N ⁢ T m , n subject ⁢ ⁢ to ⁢ : T m , n = ∑ y t = y 0 m y max m ⁢ ∑ y b = y t + 1 y max m ⁢ T y t , y b m , n y 0 m = y max ∂ 0 ⁢ ( m - 1 ) , y max m = y 0 m + ∂ 0 ⁢ ⁢ T y t , y b m , n = { 1 ∂ 1 ⁢ > ∑ i = y t y b ⁢ CB i n > ∂ 2 ∑ k = x 0 n x max n ⁢ B k , y b + 1 < ∂ 3 , x 0 n = x max ∂ 0 ⁢ ( n - 1 ) , x max n = x 0 n + ∂ 0 0 Otherwise ⁢ ⁢ CB i n = { 1 ∂ 4 ⁢ > ∑ k = x 0 n x max n ⁢ B k , i > ∂ 5 Max ⁡ ( ∑ k = x w x w + ∂ 6 ⁢ B k , i ) < ∂ 7 , x 0 n ≤ x w ≤ x max n 0 Otherwise where, ∂ 0 . . . ∂ 7 are adjustable parameters; T is the number of text strings; T y t ,y b m,n is a likelihood that a row between y t and y b in virtual block [m,n] represents text; CB i n is a likelihood that a line[i] is a part of text; and B k,i is a value of pixel[k,i] in the binary representation.
6. A computer-implemented method comprising: determining, by an anti-spam module, an approximate display location of one or more embedded images within an electronic mail (email) message; identifying, by the anti-spam module, existence of one or more abnormal factors associated with the one or more embedded images; quantifying, by the anti-spam module, a number of text strings that are included in the embedded image by analyzing one or more blocks of the binarized representation with a text string measurement algorithm; classifying, by the anti-spam module, the email message as spam or clean based on the approximate display location, the existence of one or more abnormal factors and the number of text strings; wherein the anti-spam module is implemented in one or more processors and one or more non-transitory computer-readable storage media of one or more computer systems, the one or more non-transitory computer-readable storage media having instructions tangibly embodied therein representing the anti-spam module that are executable by the one or more processors; and wherein the one or more blocks comprise M×N virtual blocks and wherein the text string measurement algorithm employs equations having a general form as follows: T = ∑ m = 0 M ⁢ ∑ n = 0 N ⁢ T m , n subject ⁢ ⁢ to ⁢ : T m , n = ∑ y t = y 0 m y max m ⁢ ∑ y b = y t + 1 y max m ⁢ T y t , y b m , n y 0 m = y max ∂ 0 ⁢ ( m - 1 ) , y max m = y 0 m + ∂ 0 ⁢ ⁢ T y t , y b m , n = { 1 ∂ 1 ⁢ > ∑ i = y t y b ⁢ CB i n > ∂ 2 ∑ k = x 0 n x max n ⁢ B k , y b + 1 < ∂ 3 , x 0 n = x max ∂ 0 ⁢ ( n - 1 ) , x max n = x 0 n + ∂ 0 0 Otherwise ⁢ ⁢ CB i n = { 1 ∂ 4 ⁢ > ∑ k = x 0 n x max n ⁢ B k , i > ∂ 5 Max ⁡ ( ∑ k = x w x w + ∂ 6 ⁢ B k , i ) < ∂ 7 , x 0 n ≤ x w ≤ x max n 0 Otherwise where, ∂ 0 . . . ∂ 7 are adjustable parameters; T is the number of text strings; T y t ,y b m,n is a likelihood that a row between y t and y b in virtual block [m,n] represents text; CB i n is a likelihood that a line[i] is a part of text; and B k,i is a value of pixel[k,i] in the binary representation. 12. The method of claim 6 , wherein a portion of the text included in the one or more embedded images comprises dark text in the context of a light background.