Mac Pro with Server 10.8.5 Randomly Shuts Down

Question

OK all you really smart dudes ...
I have a Mac Pro (2.8 GHz Quad-Core Intel Xeon) with 24GB RAM. We are running Mountain Lion Server (10.8.5) without problems until the last two weeks. "Out of the blue" in the middle of the day, it just turns off. We check on it and it is completely off and we have to restart it. Today it happened for the 3rd time ...
I pulled the System Log from the Server App (like I would know what I was looking for) and saw some suspicious activity:
Oct 24 01:20:36 [our server] sshd[75316]: Did not receive identification string from 212.129.39.8
Oct 24 01:20:37 [our server] sshd[75317]: Invalid user oracle from 212.129.39.8
Oct 24 01:20:37 [our server] sshd[75317]: input_userauth_request: invalid user oracle [preauth]
Oct 24 01:20:37 [our server] sshd[75319]: in od_record_create(): failed: 13
Oct 24 01:20:37 [our server] sshd[75319]: in od_record_create_cstring(): failed: 13
Oct 24 01:20:37 [our server] sshd[75317]: Postponed keyboard-interactive for invalid user oracle from 212.129.39.8 port 62721 ssh2 [preauth]
Oct 24 01:20:37 [our server] sshd[75319]: in od_record_create(): failed: 13
Oct 24 01:20:37 [our server] sshd[75319]: in od_record_create_cstring(): failed: 13
Oct 24 01:20:37 [our server] sshd[75319]: in pam_sm_authenticate(): OpenDirectory - Unable to get user record.
Oct 24 01:20:37 [our server] sshd[75317]: error: PAM: unknown user for illegal user oracle from 212-129-39-8.rev.poneytelecom.eu via 10.0.1.254
Oct 24 01:20:37 [our server] sshd[75317]: Failed keyboard-interactive/pam for invalid user oracle from 212.129.39.8 port 62721 ssh2
Oct 24 01:20:37 [our server] sshd[75321]: in od_record_create(): failed: 13
Oct 24 01:20:37 [our server] sshd[75321]: in od_record_create_cstring(): failed: 13
Oct 24 01:20:37 [our server] sshd[75317]: Postponed keyboard-interactive for invalid user oracle from 212.129.39.8 port 62721 ssh2 [preauth]
Oct 24 01:20:37 [our server] sshd[75321]: in od_record_create(): failed: 13
Oct 24 01:20:37 [our server] sshd[75321]: in od_record_create_cstring(): failed: 13
Oct 24 01:20:37 [our server] sshd[75321]: in pam_sm_authenticate(): OpenDirectory - Unable to get user record.
Oct 24 01:20:37 [our server] sshd[75317]: error: PAM: unknown user for illegal user oracle from 212-129-39-8.rev.poneytelecom.eu via 10.0.1.254
Oct 24 01:20:37 [our server] sshd[75317]: Failed keyboard-interactive/pam for invalid user oracle from 212.129.39.8 port 62721 ssh2
Oct 24 01:20:38 [our server] sshd[75317]: Received disconnect from 212.129.39.8: 3: com.jcraft.jsch.JSchException: Auth cancel [preauth]
Oct 24 01:23:37 [our server] servermgrd[75310]: No requests in 300 seconds, shutting down
Oct 24 01:28:20 [our server] sshd[75323]: reverse mapping checking getaddrinfo for nsg-static-198.107.71.182.airtel.in [182.71.107.198] failed - POSSIBLE BREAK-IN ATTEMPT!
Obviously, this is not the entire System log ... and the above may not have anything to do with the mystery shut downs. So here is the code from immediately before the Shut down:
Oct 24 12:26:39 [our server] bootpd[78181]: DHCP REQUEST [en0]: 1,d8:cf:9c:d4:99:5c <AndrewJnsiPhone>
Oct 24 12:26:39 [our server] bootpd[78181]: ACK sent AndrewJnsiPhone 10.0.1.100 pktsize 338
Oct 24 12:26:40 s [our server] com.apple.SecurityServer[19]: Succeeded authorizing right 'system.privilege.admin' by client '/Applications/Server.app/Contents/ServerRoot/usr/libexec/ServerEventAgent' [132] for authorization created by '/Applications/Server.app/Contents/ServerRoot/usr/libexec/ServerEventAgent' [132] (2,0)
Oct 24 12:26:40 [our server] com.apple.SecurityServer[19]: Succeeded authorizing right 'system.privilege.admin' by client '/Library/PrivilegedHelperTools/com.apple.serverd' [125] for authorization created by '/Applications/Server.app/Contents/ServerRoot/usr/libexec/ServerEventAgent' [132] (100000,0)
Oct 24 12:27:44 [our server] bootpd[78181]: DHCP REQUEST [en0]: 1,b8:e8:56:f1:b3:b5 <BenJohnnsiPhone>
Oct 24 12:27:44 [our server] bootpd[78181]: ACK sent BenJohnnsiPhone 10.0.1.71 pktsize 338
Oct 24 12:27:45 [our server] com.apple.SecurityServer[19]: Succeeded authorizing right 'system.privilege.admin' by client '/Applications/Server.app/Contents/ServerRoot/usr/libexec/ServerEventAgent' [132] for authorization created by '/Applications/Server.app/Contents/ServerRoot/usr/libexec/ServerEventAgent' [132] (2,0)
Oct 24 12:27:45 [our server] com.apple.SecurityServer[19]: Succeeded authorizing right 'system.privilege.admin' by client '/Library/PrivilegedHelperTools/com.apple.serverd' [125] for authorization created by '/Applications/Server.app/Contents/ServerRoot/usr/libexec/ServerEventAgent' [132] (100000,0)
Oct 24 14:32:48 localhost bootlog[0]: BOOT_TIME 1414179168 0
Oct 24 14:32:48 localhost com.apple.launchd[1]: *** launchd[1] has started up. ***
Oct 24 14:32:48 localhost com.apple.launchd[1]: *** Shutdown logging is enabled. ***
Can anyone determine why it is shutting down and what I need to do about it? I have ALL the System Log for the day, if that would be helpful.
Thanks.

Answer 1

Make sure there are no scheduled shutdown events in the Energy Saver preference pane. If there are not, then see below.
These instructions must be carried out as an administrator. If you have only one user account, you are the administrator.
This procedure is a diagnostic test. It makes no changes to your data.
Please triple-click anywhere in the line below on this page to select it:
syslog -k Sender kernel -k Message CSeq 'n Cause: -' | tail | awk '/:/{$4=""; print}' | pbcopy
Copy the selected text to the Clipboard by pressing the key combination command-C.
Launch the built-in Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window by pressing the key combination command-V. I've tested these instructions only with the Safari web browser. If you use another browser, you may have to press the return key after pasting.
Wait for a new line ending in a dollar sign ($) to appear below what you entered.
The output of the command will be automatically copied to the Clipboard. If the command produced no output, the Clipboard will be empty. Paste into a reply to this message.
The Terminal window doesn't show the output. Please don't copy anything from there.