can I improve my iMac security and how to get rid of remote service

I tried to change password first by getting out of network. But my message monitor show these messages. I did not do anything just watch the message monitor posting for these following messages:

2/7/16 10:33:20.546 AM configd[49]: network changed: v4(en0-:192.168.1.160) DNS- Proxy-

2/7/16 10:33:20.905 AM symptomsd[183]: __73-[NetworkAnalyticsEngine observeValueForKeyPath:ofObject:change:context:]_block_invoke unexpected switch value

2/7/16 10:40:14.000 AM kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, Symmetric flow-control, Debug [796d,0321,0de1,0300,cde1,3c00] 2/7/16 10:40:14.408 AM configd[49]: network changed: v4(en0+:192.168.1.160) DNS+ Proxy+ SMB

2/7/16 10:40:14.740 AM symptomsd[183]: __73-[NetworkAnalyticsEngine observeValueForKeyPath:ofObject:change:context:]_block_invoke unexpected switch value

When I tried to type the new password, this following message shows up:

2 22/7/16 10:37:13.343 AM com.apple.preferences.users.remoteservice[491]: becomeFirstResponder imageRect.size:{{259, 1}, {279, 22}}

I did not finish password. I look at my wifi and that was not on. the message monitor continue to post the followings;

2/7/16 10:38:04.686 AM com.apple.preferences.users.remoteservice[491]: becomeFirstResponder imageRect.size:{{259, 1}, {279, 22}}

2/7/16 10:40:14.000 AM kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, Symmetric flow-control, Debug [796d,0321,0de1,0300,cde1,3c00] 2/7/16 10:40:14.408 AM configd[49]: network changed: v4(en0+:192.168.1.160) DNS+ Proxy+ SMB

2/7/16 10:40:14.740 AM symptomsd[183]: __73-[NetworkAnalyticsEngine observeValueForKeyPath:ofObject:change:context:]_block_invoke unexpected switch value 2 2/7/16 10:40:20.485 AM sandboxd[127]: ([534]) com.apple.Safari(534) deny mach-lookup com.apple.CoreServices.coreservicesd

2/7/16 10:40:20.492 AM sandboxd[127]: ([534]) com.apple.Safari(534) deny file-read-metadata

/usr

2/7/16 10:41:03.428 AM com.apple.xpc.launchd[1]: (com.apple.WebKit.WebContent.4D2F6E2F-21E2-4E5B-AB9C-28C214685E18[535]) Service exited with abnormal code: 1

2/7/16 10:43:34.642 AM com.apple.Safari.SearchHelper[542]: Failed to obtain sandbox extension for path=/Users/guestworker/Library/Caches/com.apple.Safari.SearchHelper. Errno:1

2/7/16 10:43:34.646 AM com.apple.Safari.SearchHelper[542]: Failed to obtain sandbox extension for path=/Users/guestworker/Library/Caches/com.apple.Safari.SearchHelper. Errno:1

2/7/16 10:43:34.667 AM com.apple.SecurityServer[75]: Session 100021 created

2/7/16 10:43:34.810 AM sandboxd[127]: ([542]) com.apple.Safari(542) deny file-issue-extension /Users/guestworker/Library/Caches/com.apple.Safari.SearchHelper 2/7/16 10:43:34.816 AM sandboxd[127]: ([542]) com.apple.Safari(542) deny file-issue-extension /Users/guestworker/Library/Caches/com.apple.Safari.SearchHelper 2/7/16 10:46:46.708 AM ntpd[172]: drift PPM:39.108 -> 929.733

I know my iMac has been hacked and I have reset the computer with apple tech many times but then a few days later the computer will act up again with many remote services. Any ideas how to improve security and remove all other users connecting to this computer. my husband and I are the only users and there should not be other computers connecting to this one.