[Snort-users] ftp_pp: FTP malformed parameter

Jason Wallace jason.r.wallace at ...11827...
Thu Apr 29 12:44:54 EDT 2010


Hi,

Just migrated to 2.8.6 and I'm seeing a ton of "ftp_pp: FTP malformed
parameter" alerts in BASE.

I'm using the default config that came with 2.8.6 for ftp_telnet_protocol:

preprocessor ftp_telnet_protocol: ftp server default \
    def_max_param_len 100 \
    ports { 21 } \
    ftp_cmds { USER PASS ACCT CWD SDUP SMNT QUIT REIN PORT PASV TYPE
STRU MODE } \
    ftp_cmds { RETR STOR STOU APPE ALLO REST RNFR RNTO ABOR DELE RMD MKD PWD } \
    ftp_cmds { LIST NLST SITE SYST STAT HELP NOOP } \
    ftp_cmds { AUTH ADAT PROT PBSZ CONF ENC } \
    ftp_cmds { FEAT OPTS CEL CMD MACB } \
    ftp_cmds { MDTM REST SIZE MLST MLSD } \
    ftp_cmds { XPWD XCWD XCUP XMKD XRMD TEST CLNT } \
    alt_max_param_len 0 { CDUP QUIT REIN PASV STOU ABOR PWD SYST NOOP } \
    alt_max_param_len 100 { MDTM CEL XCWD SITE USER PASS REST DELE RMD
SYST TEST STAT MACB EPSV CLNT LPRT } \
    alt_max_param_len 200 { XMKD NLST ALLO STOU APPE RETR STOR CMD RNFR HELP } \
    alt_max_param_len 256 { RNTO CWD } \
    alt_max_param_len 400 { PORT } \
    alt_max_param_len 512 { SIZE } \
    chk_str_fmt { USER PASS ACCT CWD SDUP SMNT PORT TYPE STRU MODE } \
    chk_str_fmt { RETR STOR STOU APPE ALLO REST RNFR RNTO DELE RMD MKD } \
    chk_str_fmt { LIST NLST SITE SYST STAT HELP } \
    chk_str_fmt { AUTH ADAT PROT PBSZ CONF ENC } \
    chk_str_fmt { FEAT OPTS CEL CMD } \
    chk_str_fmt { MDTM REST SIZE MLST MLSD } \
    chk_str_fmt { XPWD XCWD XCUP XMKD XRMD TEST CLNT } \
    cmd_validity MODE < char ASBCZ > \
    cmd_validity STRU < char FRP > \
    cmd_validity ALLO < int [ char R int ] > \
    cmd_validity TYPE < { char AE [ char NTC ] | char I | char L [
number ] } > \
    cmd_validity MDTM < [ date nnnnnnnnnnnnnn[.n[n[n]]] ] string > \
    cmd_validity PORT < host_port >
#
preprocessor ftp_telnet_protocol: ftp client default \
    max_resp_len 256 \
    bounce yes \
    telnet_cmds yes


Here are some examples from BASE of what is triggering the alerts...


length = 6

000 : 4E 4C 53 54 0D 0A                                 NLST..


length = 14

000 : 4F 50 54 53 20 75 74 66 38 20 6F 6E 0D 0A         OPTS utf8 on..


There are also a lot of these...

length = 6

000 : 53 59 53 54 0D 0A                                 SYST..



It all looks like legit traffic. Is it chk_str_fmt that is causing
these? If so why are they triggering?

Thx,
Wally




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