GEN:SID | 1:1883 |
Message | ATTACK-RESPONSES id check returned nobody |
Summary | This rule has been placed in deleted.rules
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Impact | attacker might have gained an ability to execute commands remotely on the system.
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Detailed Information | This signature triggers when a UNIX "id" command is used to confirm the user name of the currently logged in user over any unencrypted connection. Such connection can be either a legitimate telnet connection or a result of spawning a shell on FTP, POP3, SMTP or other port as a consequence of network exploit. The string "uid=" and "(nobody)" is an output of an "id" command indicating that the user has "nobody" account privileges, typically used by the web server process. Seeing such a response indicates that some user connected over the network to a target web server and likely exploited the web server to launch a shell.
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Affected Systems | |
Attack Scenarios | a buffer overflow exploit against the WWW server results in "/bin/sh" being executed. An automated script performing an attack, checks for the success of the exploit via an "id" command.
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Ease of Attack | this post-attack behavior can accompany different attacks
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Corrective Action | investigate the server for signs of compromise, run the integrity checking software, look for other IDS alerts involving the same IP addresses.
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Additional References | |