Sorry, I'm not sure that I've gone the right way about getting this report into the system. Didn't know whether I should have amended the original post, but I'll learn.
Here is the EtreCheck report. The Symantec AV expired 12 months ago, long before the trouble started, and I didn't run the cleaning app until well after the crashes started, so I can't really see them being the problem.
EtreCheck version: 2.6.6 (226)
Report generated 1/01/2016, 11:03
Runtime 4:48
Download EtreCheck from http://etrecheck.com
Click the [Click for support] links for help with non-Apple products.
Click the [Click for details] links for more information about that line.
Click the [Click to remove] links for help removing adware.
Hardware Information: (What does this mean?)
iMac (21.5-inch, Late 2012)
[Click for Technical Specifications]
[Click for User Guide]
iMac - model: iMac13,1
1 2.7 GHz Intel Core i5 CPU: 4-core
8 GB RAM Upgradeable
[Click for upgrade instructions]
BANK 0/DIMM0
4 GB DDR3 1600 MHz ok
BANK 1/DIMM0
4 GB DDR3 1600 MHz ok
Bluetooth: Good - Handoff/Airdrop2 supported
Wireless: en1: 802.11 a/b/g/n
Video Information: (What does this mean?)
NVIDIA GeForce GT 640M - VRAM: 512 MB
iMac 1920 x 1080
System Software: (What does this mean?)
OS X El Capitan 10.11.1 (15B42) - Time since boot: less than an hour
Disk Information: (What does this mean?)
APPLE HDD ST1000LM024 disk0 : (1 TB) (Rotational)
EFI (disk0s1) <not mounted> : 210 MB
MacIntoshHD (disk0s2) / : 999.35 GB (571.08 GB free)
Recovery HD (disk0s3) <not mounted> [Recovery]: 650 MB
USB Information: (What does this mean?)
Apple Inc. FaceTime HD Camera (Built-in)
Apple Inc. BRCM20702 Hub
Apple Inc. Bluetooth USB Host Controller
Western Digital External HDD 640.14 GB
EFI (disk2s1) <not mounted> : 210 MB
WDTimemachineBU (disk2s2) /Volumes/WDTimemachineBU : 639.79 GB (518.58 GB free)
Lexar USB Flash Drive 3.95 GB
ESD-USB (disk3s1) /Volumes/ESD-USB : 3.95 GB (3.84 GB free)
Verbatim STORE N GO 15.62 GB
UUI (disk1s1) /Volumes/UUI : 15.62 GB (13.50 GB free)
Thunderbolt Information: (What does this mean?)
Apple Inc. thunderbolt_bus
Gatekeeper: (What does this mean?)
Mac App Store and identified developers
Kernel Extensions: (What does this mean?)
/Library/Extensions
[not loaded] com.symantec.kext.SymAPComm (12.7.1f4 - SDK 10.8) [Click for support]
[not loaded] com.symantec.kext.fw (5.3.1f4 - SDK 10.8) [Click for support]
[loaded] com.symantec.kext.internetSecurity (5.4f4 - SDK 10.8) [Click for support]
[loaded] com.symantec.kext.ips (3.9.2f1 - SDK 10.8) [Click for support]
[loaded] com.symantec.kext.pf (5.7.1f4 - SDK 10.8) [Click for support]
/System/Library/Extensions
[not loaded] com.wdc.driver.1394.64.10.9 (1.0.1 - SDK 10.9) [Click for support]
[not loaded] com.wdc.driver.USB.64.10.9 (1.0.1 - SDK 10.9) [Click for support]
Launch Agents: (What does this mean?)
[loaded] com.google.keystone.agent.plist [Click for support]
[loaded] com.oracle.java.Java-Updater.plist [Click for support]
Launch Daemons: (What does this mean?)
[loaded] com.adobe.fpsaud.plist [Click for support]
[loaded] com.barebones.authd.plist [Click for support]
[loaded] com.google.keystone.daemon.plist [Click for support]
[loaded] com.oracle.java.Helper-Tool.plist [Click for support]
[loaded] com.wdc.WDPrivilegedHelper.plist [Click for support]
User Launch Agents: (What does this mean?)
[loaded] com.divx.agent.postinstall.plist [Click for support]
User Login Items: (What does this mean?)
iTunesHelper Application (/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)
WDDriveUtilityHelper UNKNOWN (missing value)
WD Quick View UNKNOWN (missing value)
Other Apps: (What does this mean?)
[running] com.apple.xpc.launchd.oneshot.0x10000003.EtreCheck
Internet Plug-ins: (What does this mean?)
FlashPlayer-10.6: Version: 20.0.0.267 - SDK 10.6 [Click for support]
QuickTime Plugin: Version: 7.7.3
Flash Player: Version: 20.0.0.267 - SDK 10.6 [Click for support]
JavaAppletPlugin: Version: Java 8 Update 66 build 17 Check version
Default Browser: Version: 601 - SDK 10.11
User internet Plug-ins: (What does this mean?)
Google Earth Web Plug-in: Version: 7.1 [Click for support]
Safari Extensions: (What does this mean?)
GoPhoto.it Adware! [Click to remove]
DivX Plus Web Player HTML5 <video>
3rd Party Preference Panes: (What does this mean?)
Flash Player [Click for support]
Java [Click for support]
Time Machine: (What does this mean?)
Skip System Files: NO
Mobile backups: OFF
Auto backup: YES
Volumes being backed up:
MacIntoshHD: Disk size: 999.35 GB Disk used: 428.26 GB
Destinations:
WDTimemachineBU [Local]
Total size: 639.79 GB
Total number of backups: 22
Oldest backup: 13/12/2015, 07:07
Last backup: 31/12/2015, 16:42
Size of backup disk: Too small
Backup size 639.79 GB < (Disk used 428.26 GB X 3)
Top Processes by CPU: (What does this mean?)
21% com.apple.WebKit.WebContent
10% WindowServer
3% kernel_task
2% com.apple.WebKit.Networking
1% syncdefaultsd
Top Processes by Memory: (What does this mean?)
733 MB kernel_task
279 MB mdworker(19)
115 MB ocspd
98 MB mds_stores
74 MB WindowServer
Virtual Memory Information: (What does this mean?)
4.99 GB Free RAM
3.00 GB Used RAM (1.28 GB Cached)
0 B Swap Used
Diagnostics Information: (What does this mean?)
Jan 1, 2016, 10:51:06 AM Self test - passed
Dec 31, 2015, 05:39:54 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-31-173954_[redacted].panic [Click for details]
Dec 31, 2015, 02:43:13 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-31-144313_[redacted].panic [Click for details]
Dec 31, 2015, 01:05:46 PM ~/Library/Logs/DiagnosticReports/Finder_2015-12-31-130546_[redacted].crash
Dec 29, 2015, 05:02:00 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-29-170200_[redacted].panic [Click for details]
Dec 29, 2015, 03:48:12 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-29-154812_[redacted].panic [Click for details]
Dec 29, 2015, 02:10:35 PM ~/Library/Logs/DiagnosticReports/Xcode_2015-12-29-141035_[redacted].crash
Dec 29, 2015, 01:18:05 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-29-131805_[redacted].panic [Click for details]
Dec 29, 2015, 11:03:31 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-29-110331_[redacted].panic [Click for details]
Dec 28, 2015, 10:04:07 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-28-220407_[redacted].panic [Click for details]
Dec 28, 2015, 05:32:04 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-28-173204_[redacted].panic [Click for details]
Dec 28, 2015, 11:59:37 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-28-115937_[redacted].panic [Click for details]
Dec 28, 2015, 11:20:23 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-28-112023_[redacted].panic [Click for details]
Dec 27, 2015, 08:25:24 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-27-202524_[redacted].panic [Click for details]
Dec 27, 2015, 05:56:43 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-27-175643_[redacted].panic [Click for details]
Dec 27, 2015, 02:00:41 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-27-140041_[redacted].panic [Click for details]
Dec 27, 2015, 12:16:47 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-27-121647_[redacted].panic [Click for details]
Dec 27, 2015, 11:41:08 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-27-114108_[redacted].panic [Click for details]
Dec 26, 2015, 05:02:44 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-26-170244_[redacted].panic [Click for details]
Dec 26, 2015, 12:56:18 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-26-125618_[redacted].panic [Click for details]
Dec 26, 2015, 09:41:42 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-26-094142_[redacted].panic [Click for details]
Dec 25, 2015, 07:35:25 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-25-193525_[redacted].panic [Click for details]
Dec 25, 2015, 05:05:59 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-25-170559_[redacted].panic [Click for details]
Dec 25, 2015, 11:34:46 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-25-113446_[redacted].panic [Click for details]
Dec 24, 2015, 01:49:42 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-24-134942_[redacted].panic [Click for details]
Dec 23, 2015, 07:05:12 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-23-190512_[redacted].panic [Click for details]
Dec 23, 2015, 04:34:57 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-23-163457_[redacted].panic [Click for details]
Dec 23, 2015, 02:41:25 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-23-144125_[redacted].panic [Click for details]
Dec 23, 2015, 12:25:54 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-23-122554_[redacted].panic [Click for details]
Dec 22, 2015, 11:02:46 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-22-110246_[redacted].panic [Click for details]
Dec 18, 2015, 04:56:04 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-18-165604_[redacted].panic [Click for details]
Dec 17, 2015, 04:23:04 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-17-162304_[redacted].panic [Click for details]
Dec 17, 2015, 02:49:05 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-17-144905_[redacted].panic [Click for details]
Dec 17, 2015, 10:51:27 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-17-105127_[redacted].panic [Click for details]
Dec 16, 2015, 03:28:10 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-16-152810_[redacted].panic [Click for details]
Dec 16, 2015, 11:49:50 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-16-114950_[redacted].panic [Click for details]
Dec 16, 2015, 09:34:30 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-16-093430_[redacted].panic [Click for details]
Dec 15, 2015, 04:57:49 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-15-165749_[redacted].panic [Click for details]
Dec 15, 2015, 11:56:50 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-15-115650_[redacted].panic [Click for details]
Dec 15, 2015, 11:08:59 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-15-110859_[redacted].panic [Click for details]
Dec 14, 2015, 05:17:08 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-14-171708_[redacted].panic [Click for details]
Dec 14, 2015, 03:12:50 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-14-151250_[redacted].panic [Click for details]
Dec 13, 2015, 05:14:38 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-13-171438_[redacted].panic [Click for details]
Dec 13, 2015, 12:55:04 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-13-125504_[redacted].panic [Click for details]
Dec 13, 2015, 10:47:23 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-13-104723_[redacted].panic [Click for details]
Dec 12, 2015, 09:29:16 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-12-212916_[redacted].panic [Click for details]
Dec 12, 2015, 06:16:47 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-12-181647_[redacted].panic [Click for details]
Dec 12, 2015, 11:14:35 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-12-111435_[redacted].panic [Click for details]
Dec 11, 2015, 06:35:24 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-11-183524_[redacted].panic [Click for details]
Dec 11, 2015, 03:42:55 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-11-154255_[redacted].panic [Click for details]
Dec 11, 2015, 12:57:54 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-11-125754_[redacted].panic [Click for details]
Dec 11, 2015, 12:29:29 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-11-122929_[redacted].panic [Click for details]
Dec 11, 2015, 10:18:46 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-11-101846_[redacted].panic [Click for details]
Dec 10, 2015, 08:40:16 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-10-204016_[redacted].panic [Click for details]
Dec 10, 2015, 05:41:44 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-10-174144_[redacted].panic [Click for details]
Dec 10, 2015, 03:35:48 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-10-153548_[redacted].panic [Click for details]
Dec 10, 2015, 02:16:51 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-10-141651_[redacted].panic [Click for details]
Dec 10, 2015, 12:12:38 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-10-121238_[redacted].panic [Click for details]
Dec 9, 2015, 05:01:59 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-09-170159_[redacted].panic [Click for details]
Dec 9, 2015, 02:53:37 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-09-145337_[redacted].panic [Click for details]
Dec 7, 2015, 08:43:08 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-07-204308_[redacted].panic [Click for details]
Dec 7, 2015, 05:46:15 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-07-174615_[redacted].panic [Click for details]
Dec 7, 2015, 05:09:34 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-07-170934_[redacted].panic [Click for details]
Dec 6, 2015, 08:35:17 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-06-203517_[redacted].panic [Click for details]
Dec 6, 2015, 01:49:13 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-06-134913_[redacted].panic [Click for details]
Dec 6, 2015, 11:42:27 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-06-114227_[redacted].panic [Click for details]
Dec 4, 2015, 12:28:52 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-04-122852_[redacted].panic [Click for details]
Dec 3, 2015, 10:29:29 AM /Library/Logs/DiagnosticReports/Kernel_2015-12-03-102929_[redacted].panic [Click for details]
Dec 2, 2015, 05:07:55 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-02-170755_[redacted].panic [Click for details]
Dec 2, 2015, 03:17:06 PM /Library/Logs/DiagnosticReports/Kernel_2015-12-02-151706_[redacted].panic [Click for details]