Introduction to Ngrep

    Date10 Jan 2003
    4266
    Posted ByAnthony Pell
    During the source of investigating the wu-ftpd exploit (see references), analysts were reminded of the one of the limitations of current Intrusion Detection Systems; the inability to handle regular expressions. When the attack has identifiable fixed strings of characters, the signature . . . During the source of investigating the wu-ftpd exploit (see references), analysts were reminded of the one of the limitations of current Intrusion Detection Systems; the inability to handle regular expressions. When the attack has identifiable fixed strings of characters, the signature is reasonably straightforward.

    The problem comes when we don't have a fixed series of characters to match against. The November 2001 wu-ftpd exploit used the fact that a sequence of whitespace, a tilde, optional characters, a left curly brace, and any other characters without a matching right curly brace would crash wu-ftpd, allowing a buffer overflow exploit to take over.

    Because of the possibility of additional characters and the requirement that the second block of characters not contain a "}", we need to use something stronger than fixed strings.

    You are not authorised to post comments.

    Comments powered by CComment

    LinuxSecurity Poll

    Do you read our distribution advisories on a regular basis?

    No answer selected. Please try again.
    Please select either existing option or enter your own, however not both.
    Please select minimum 0 answer(s) and maximum 3 answer(s).
    /component/communitypolls/?task=poll.vote&format=json
    23
    radio
    [{"id":"84","title":"Yes, for a single distribution","votes":"0","type":"x","order":"1","pct":0,"resources":[]},{"id":"85","title":"Yes, for multiple distributions","votes":"5","type":"x","order":"2","pct":71.43,"resources":[]},{"id":"86","title":"No","votes":"2","type":"x","order":"3","pct":28.57,"resources":[]}]["#ff5b00","#4ac0f2","#b80028","#eef66c","#60bb22","#b96a9a","#62c2cc"]["rgba(255,91,0,0.7)","rgba(74,192,242,0.7)","rgba(184,0,40,0.7)","rgba(238,246,108,0.7)","rgba(96,187,34,0.7)","rgba(185,106,154,0.7)","rgba(98,194,204,0.7)"]350
    bottom200

    We use cookies to provide and improve our services. By using our site, you consent to our Cookie Policy.