Many steganographic systems are weak against visual and statistical attacks. Systems without these weaknesses offer only a relatively small capacity for steganographic messages. The newly developed algorithm F5 withstands visual and statistical attacks, yet it still offers a large steganographic capacity. F5 implements matrix encoding to improve the efficiency of embedding. Thus it reduces the number of necessary changes. F5 employs permutative straddling to uniformly spread out the changes over the whole steganogram.
Secure steganographic algorithms hide confidential messages within other, more extensive data (carrier media). An attacker should not be able to find out, that something is embedded in the steganogram (i. e., a steganographically modified carrier medium) Visual attacks on steganographic systems are based on essential information in the carrier medium that steganographic algorithms overwrite . Adaptive techniques (that bring the embedding rate in line with the carrier content) prevent visual attacks, however, they also reduce the proportion of steganographic information in a carrier medium. Lossy compressed carrier media (JPEG,MP3, . . . ) are originally adaptive and immune against visual (and auditory respectively) attacks.
The steganographic tool Jsteg  embeds messages in lossy compressed JPEG files. It has a high capacity—e. g., 12 % of the steganogram’s size—and, it is immune against visual attacks. However, a statistical attack discovers changes made by Jsteg . MP3Stego  and IVS-Stego  also withstand auditory and visual attacks respectively. Appart from this, the extremely low embedding rate prevents all known statistical attacks. These two steganographic tools offer only a relatively small capacity for steganographic messages (less than 1 % of the steganogram’s size).