Weird Split-Second Flash on iMac Screen

I did run the Etrecheck program. As I was directed by Etrecheck to submit the report back to the Support Community, I am pasting it into this reply.

EtreCheck version: 4.1 (4A162)

Report generated: 2018-03-01 17:19:23

Download EtreCheck from https://etrecheck.com

Runtime: 1:35

Performance: Excellent

Problem: Other problem

Description:

A weird split-second flash is occurring on my iMac screen. It appears to be rectangular in shape, much like a pop-up ad. It does not matter if only my desktop is showing, or if I am in Safari or any other program, it still occurs every ten minutes. It occurs so fast I cannot read any words; however, the block does appear to contain words at the top. There also appears to be a blue line across the rectangular image. The image is approximately an inch in height, and about three inches in length.

Also, Screen Sharing is turned off in my Systems Folder.

Major Issues:

Anything that appears on this list needs immediate attention.

Adware - Adware detected.

Old operating system - Old operating system versions no longer receive security updates.

Minor Issues:

These issues do not need immediate attention but they may indicate future problems.

Heavy RAM usage - This machine is using a large amount of RAM.

Clean up - There are orphan files that could be removed.

Unsigned files - There is unsigned software installed. It appears to be legitimate but should be reviewed.

32-bit Apps - This machine has 32-bits apps that may have problems in the future.

Hardware Information:

iMac (Retina 5K, 27-inch, Late 2014)

iMac Model: iMac15,1

1 4 GHz Intel Core i7 (i7-4790K) CPU: 4-core

32 RAM At maximum

BANK 0/DIMM0

8 GB DDR3 1600 ok

BANK 1/DIMM0

8 GB DDR3 1600 ok

BANK 0/DIMM1

8 GB DDR3 1600 ok

BANK 1/DIMM1

8 GB DDR3 1600 ok

Video Information:

AMD Radeon R9 M295X - VRAM: 4096 MB

iMac 5120 x 2880

Drives:

disk0 - APPLE SSD SM0512F 500.28 GB (Solid State - TRIM: Yes)

Internal PCI 5.0 GT/s x2 Serial ATA

disk0s1 - EFI [EFI] 210 MB

disk0s2 - C******r [Core Storage Container] 499.42 GB

disk1 - S*********D (Journaled HFS+) 499.10 GB

disk0s3 - Recovery HD [Recovery] 650 MB

Mounted Volumes:

disk1 - S*********D 499.10 GB (229.48 GB free)

Journaled HFS+

Mount point: /

Network:

Interface Bluetooth-Modem: Bluetooth DUN

Interface en0: Ethernet

Interface en1: Wi-Fi

802.11 a/b/g/n/ac

One IPv4 address

Interface en4: Bluetooth PAN

Interface bridge0: Thunderbolt Bridge

System Software:

OS X Yosemite 10.10.5 (14F2511)

Time since boot: Less than an hour

System Load: 1.25 (1 min ago) 1.33 (5 min ago) 1.13 (15 min ago)

Security:

Adware:

Launchd: ~/Library/LaunchAgents/pronto.update.plist

Reason: Adware name match

Executable: ~/Library/Application Support/ProntoApp/ProntoApp.app/Contents/MacOS/ProntoApp -trigger update -app_name ProntoApp

Launchd: ~/Library/LaunchAgents/Arcahol.disable.plist

Reason: Adware name match

Executable: ~/Library/Application Support/Arcahol/Arcahol.app/Contents/MacOS/AppIR -trigger disable -isDev 0 -installVersion 1054 -firstAppId 1496565238047945 -identity Arcahol

Launchd: ~/Library/LaunchAgents/pronto.notification.plist

Reason: Adware name match

Executable: ~/Library/Application Support/ProntoApp/ProntoApp.app/Contents/MacOS/ProntoApp -trigger notification -app_name ProntoApp -emid 584ab0e9a2aa5e2a4a077867c367bd4d

Launchd: ~/Library/LaunchAgents/Smokyashan.update.plist

Reason: Adware name match

Executable: ~/Library/Application Support/Smokyashan/Smokyashan.app/Contents/MacOS/AppNOS -trigger update -isDev 0 -installVersion 861 -firstAppId 1434976216979282 -identity Smokyashan -sig NOSIGNATURE_SIGNATURE -agentUpdate 2

Launchd: ~/Library/LaunchAgents/Arcahol.AppVemoral.plist

Reason: Adware name match

Executable: ~/Library/Application Support/Arcahol/Arcahol.app/Contents/MacOS/AppIR -trigger AppRemoval -isDev 0 -installVersion 1054 -firstAppId 1496565238047945 -identity Arcahol

Launchd: ~/Library/LaunchAgents/Arcahol.uadpte.plist

Reason: Adware name match

Executable: ~/Library/Application Support/Arcahol/Arcahol.app/Contents/MacOS/AppIR -trigger update -isDev 0 -installVersion 1054 -firstAppId 1496565238047945 -identity Arcahol -sig ILAN_RAMBAM_SIGNATURE -agentUpdate 0

Launchd: ~/Library/LaunchAgents/Arcahol.dolnwoad.plist

Reason: Adware name match

Executable: ~/Library/Application Support/Arcahol/Arcahol.app/Contents/MacOS/AppIR -trigger download -isDev 0 -installVersion 1054 -firstAppId 1496565238047945 -sig ILAN_RAMBAM_SIGNATURE -identity Arcahol

Launchd: ~/Library/LaunchAgents/Arcahol.btvlit.plist

Reason: Adware name match

Executable: ~/Library/Application Support/Arcahol/Arcahol.app/Contents/MacOS/AppIR -trigger ltvbit -isDev 0 -installVersion 1054 -firstAppId 1496565238047945 -identity Arcahol

Safari Extension: Smokyashan

Reason: Adware name match

Safari Extension: Arcahol

Reason: Adware name match

Unsigned Files:

Launchd: ~/Library/LaunchAgents/com.amazon.music.plist

Executable: /Applications/Amazon Music.app/Contents/MacOS/Amazon Music Helper

Details: Exact match found in the whitelist - probably OK

32-bit Applications:

Kernel Extensions:

/System/Library/Extensions

[Not Loaded] Seagate Storage Driver.kext (5.2.4 (26840) - SDK 10.4)

/System/Library/Extensions/Seagate Storage Driver.kext/Contents/PlugIns

[Not Loaded] SeagateLeafPowSecDriver_10_4.kext (5.2.4 (26840) - SDK 10.4)

[Not Loaded] SeagateLeafPowSecDriver_10_5.kext (5.2.4 (26840) - SDK 10.5)

[Not Loaded] SeagateDriveIcons.kext (5.2.4 (26840) - SDK 10.4)

System Launch Agents:

System Launch Daemons:

Launch Agents:

Launch Daemons:

User Launch Agents:

User Login Items:

iTunesHelper Application (Apple, Inc. - installed 2018-01-24)

(/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)

Canon IJ Network Scanner Selector2 Application

(/Library/Printers/Canon/IJScanner/Utilities/Canon IJ Network Scanner Selector2.app)

Backup and Sync from Google Application (Google, Inc.

(/Applications/Backup and Sync.app)

Launch Nikon Message Center 2 Application

(/Applications/Nikon Software/Nikon Message Center 2/Nikon Message Center 2.app/Contents/SharedSupport/Launch Nikon Message Center 2.app)

Dropbox Application (Dropbox, Inc.

(/Applications/Dropbox.app)

Backup and Sync from Google Application (Google, Inc.

(/Applications/Backup and Sync.app)

CIJSUAgent SMLoginItem (Canon Inc. - installed 2015-10-30)

(/Applications/Canon Utilities/IJ Scan Utility/Canon IJ Scan Utility2.app/Contents/Library/LoginItems/CIJSUAgent.app)

PhotoStreamAgent SMLoginItem (Mac App Store - installed 2038-01-18)

(/Applications/iPhoto.app/Contents/Library/LoginItems/PhotoStreamAgent.app)

Internet Plug-ins:

FlashPlayer-10.6: 28.0.0.161 (installed 2018-02-16)

QuickTime Plugin: 7.7.3 (installed 2017-07-24)

Flash Player: 28.0.0.161 (installed 2018-02-16)

PepperFlashPlayer: 28.0.0.161 (installed 2018-02-07)

AdobeAAMDetect: 3.0.0.0 (installed 2016-10-29)

Default Browser: 600 (installed 2015-08-25)

User Internet Plug-ins:

CitrixOnlineWebDeploymentPlugin: 1.0.105 (installed 2013-04-25)

Safari Extensions:

3rd Party Preference Panes:

Flash Player (installed 2018-02-01)

Seagate Dashboard for Mac OSX (installed 2015-09-01)

Time Machine:

Skip System Files: No

Mobile backups: No

Auto backup: Yes

Volumes being backed up:

S*********D: Disk size: 499.10 GB - Disk used: 269.62 GB

Destinations:

S***********************e [Local] (Last used)

Total size: 999.86 GB

Total number of backups: 45

Oldest backup: 2015-10-20 21:04:08

Last backup: 2015-12-28 14:55:37

Top Processes by CPU:

Top Processes by Memory:

Top Processes by Energy Use:

Virtual Memory Information:

Clean up:

~/Library/LaunchAgents/amUpdater.plist

/Applications/Archive Manager.app/Contents/Resources/appUpdater

Executable not found

Diagnostics Information (past 7 days):

2018-03-01 16:53:24 Last Shutdown Cause: 3 - Hard shutdown

2018-02-24 20:26:51 Adobe Lightroom.app CPU

End of report

Just an addition...there seems to be a blue line that quickly goes across the rectangular block when it flashes on. Also, when this happens, I have to click whatever screen I am on to cause it to be active again.

As this report does show adware, I know it needs to be removed. However, I am unsure how to go about this. I actually detected the Arcachol adware through Safari back when the report states that it was installed. I thought I had successfully uninstalled it, but obviously not! However, as previously stated, the "pop-up adware" has only been occurring for the past few days.

Is there any way I can get rid of this adware??

Also, with the age of my computer, is it safe to try and bring my system up to date with High Sierra?

Thank you so very much for your help!!!