unexplained port 524 probes payload "cko"

From: Fragga (fraggaat_private)
Date: Fri Jun 28 2002 - 04:39:15 PDT

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    greets incidents list,
    
    for the past couple of days i`ve noticed a methodical probe from a source to
    my server on port 524. I`m aware this is something to do with Netware
    however i`m not quite sure of their purpose. the machine sends syns to port
    524 but for some reason even though this port is not open my machine does
    not send a rst. then after 6 syns it sends two packets with both ack and rst
    set with the payload "cko". This same sequence happens every 15 minutes...
    
    Has anyone seen this before or have any idea what the point of it is ? Snort
    Dump below.
    
    thanks
    
    fragga
    
    06/28-11:46:01.721557 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3E
    195.147.191.186:5448 -> my.ip.add.ress:524 TCP TTL:112 TOS:0x0 ID:1473
    IpLen:20 DgmLen:48 DF
    ******S* Seq: 0x3A18F81C  Ack: 0x0  Win: 0x2000  TcpLen: 28
    TCP Options (4) => MSS: 1460 NOP NOP SackOK
    
    06/28-11:46:04.625473 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3E
    195.147.191.186:5448 -> my.ip.add.ress:524 TCP TTL:112 TOS:0x0 ID:10433
    IpLen:20 DgmLen:48 DF
    ******S* Seq: 0x3A18F81C  Ack: 0x0  Win: 0x2000  TcpLen: 28
    TCP Options (4) => MSS: 1460 NOP NOP SackOK
    
    06/28-11:46:10.632395 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3E
    195.147.191.186:5448 -> my.ip.add.ress:524 TCP TTL:112 TOS:0x0 ID:21953
    IpLen:20 DgmLen:48 DF
    ******S* Seq: 0x3A18F81C  Ack: 0x0  Win: 0x2000  TcpLen: 28
    TCP Options (4) => MSS: 1460 NOP NOP SackOK
    
    06/28-11:46:31.166756 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3E
    195.147.191.186:5384 -> my.ip.add.ress:524 TCP TTL:112 TOS:0x0 ID:50547
    IpLen:20 DgmLen:48 DF
    ******S* Seq: 0xFDFF551E  Ack: 0x0  Win: 0x2000  TcpLen: 28
    TCP Options (4) => MSS: 1460 NOP NOP SackOK
    
    06/28-11:46:34.113389 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3E
    195.147.191.186:5384 -> my.ip.add.ress:524 TCP TTL:112 TOS:0x0 ID:51059
    IpLen:20 DgmLen:48 DF
    ******S* Seq: 0xFDFF551E  Ack: 0x0  Win: 0x2000  TcpLen: 28
    TCP Options (4) => MSS: 1460 NOP NOP SackOK
    
    06/28-11:46:40.113640 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3E
    195.147.191.186:5384 -> my.ip.add.ress:524 TCP TTL:112 TOS:0x0 ID:56691
    IpLen:20 DgmLen:48 DF
    ******S* Seq: 0xFDFF551E  Ack: 0x0  Win: 0x2000  TcpLen: 28
    TCP Options (4) => MSS: 1460 NOP NOP SackOK
    
    06/28-11:53:40.473109 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3C
    195.147.191.186:5448 -> my.ip.add.ress:524 TCP TTL:16 TOS:0x0 ID:0 IpLen:20
    DgmLen:43
    ***A*R** Seq: 0x0  Ack: 0x0  Win: 0x0  TcpLen: 20
    63 6B 6F                                         cko
    
    06/28-11:54:10.478336 0:8:20:E7:CC:0 -> 0:10:E0:3:2A:FC type:0x800 len:0x3C
    195.147.191.186:5384 -> my.ip.add.ress:524 TCP TTL:16 TOS:0x0 ID:0 IpLen:20
    DgmLen:43
    ***A*R** Seq: 0x0  Ack: 0x0  Win: 0x0  TcpLen: 20
    63 6B 6F                                         cko
    
    
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