Does Windows Defender Antivirus and Windows Defender Firewall keep my laptop 100% secure?


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In regard of the latest new information, would you still trust that the system is clean from malware?

New laptop
Windows 11 S
Windows S mode on
OOBE
MS Defender or McAfee LiveSafe selected as the antivirus - I believe MS Defender was the selected AV from the start
Internet connection for a couple of minutes during OOBE setup

In Windows, internet connection for a couple of minutes, just to turn S mode off
After S mode was turned off - turned off the internet connection
While having internet connection:
Did not open any internet browsers
Did not visit any websites
Did not open any emails

14 days later
Turned on internet connection
Download one software from Microsoft Store
Turned off internet connection again
While having internet connection:
Did not open any internet browsers
Did not visit any websites
Did not open any emails

Internet connection has been permanent off since

30 days later of getting the laptop
Internet connection still turned off
Deep scan with MS Defender - clean

Thank you
 

My Computer

System One

  • OS
    Windows 11
    Computer type
    Laptop
Are you any more or less confident than you were on April 7, where you posted nearly the same thing, and said, "I feel confident my system is clean because of all your great answers?" It seems to me, after 60 posts, you're never going to take comfort in your PC being clean, no matter what anyone says.
 

My Computer

System One

  • OS
    Windows 11 Pro 24H2 [rev. 4351]
    Computer type
    PC/Desktop
    Manufacturer/Model
    Intel NUC12WSHi7
    CPU
    12th Gen Intel Core i7-1260P, 2100 MHz
    Motherboard
    NUC12WSBi7
    Memory
    64 GB
    Graphics Card(s)
    Intel Iris Xe
    Sound Card
    built-in Realtek HD audio
    Monitor(s) Displays
    Dell U3219Q
    Screen Resolution
    3840x2160 @ 60Hz
    Hard Drives
    Samsung SSD 990 PRO 1TB
    Keyboard
    CODE 104-Key Mechanical with Cherry MX Clears
    Antivirus
    Microsoft Defender
Are you any more or less confident than you were on April 7, where you posted nearly the same thing, and said, "I feel confident my system is clean because of all your great answers?" It seems to me, after 60 posts, you're never going to take comfort in your PC being clean, no matter what anyone says.
I had hoped for some confirmation or directions for what else I could research to make sure my system is clean

Thank you
 

My Computer

System One

  • OS
    Windows 11
    Computer type
    Laptop
If the more serious contributors in this forum haven't met your criteria for providing a convincing argument, then next logical steps are:

1. Find a different forum community that you accept as more knowledgeable on security questions. For example, Wilders Security forum or SysNative.
2. Find input from a recognized Windows security researcher, who is a professional.
3. Do your own testing until you're satisfied with the results.

You're asking other folks to confirm a scenario which we can't reproduce. We know how to clean install Windows, we know how to enable S mode. We don't know how your specific PC was shipped from the factory, and what software or changes were applied there. McAfee is a 3rd-party app.

The only way to reproduce this is to order another new PC from your vendor, don't boot it up, but remove the system disk and mount it on another PC. Clone the untouched drive using a disk cloning tool as block-accurate copy, and perform a set of experiments on the cloned image until you're finally satisfied with the investigation. Reset the PC between tests, by restoring your disk from the cloned image.

This is what real security researchers do, they test things to find out what's actually true.
 

My Computer

System One

  • OS
    Windows 7
Many windows users feel that Windows Security is enough for a standalone antivirus/internet security suite.
 

My Computers

System One System Two

  • OS
    MacOS Monterey (Windows 10 via Parallels)
    Computer type
    Laptop
    Manufacturer/Model
    MacOS
    CPU
    Core i3 processor
    Motherboard
    Macintosh
    Memory
    8gb
    Graphics Card(s)
    Intel® Integrated SoC
    Sound Card
    Realtek HD Audio Driver
    Screen Resolution
    15.6"
    Hard Drives
    256GB M.2 SSD
    Mouse
    Custom Wireless Mouse
    Internet Speed
    256 mbps DL 8-10 mbps UL
    Browser
    Mozilla Firefox
    Antivirus
    Avira AntiVirus
  • Operating System
    Windows 11 2242 Professional
    Computer type
    Laptop
    Manufacturer/Model
    Jumper
    CPU
    Intel i8 Processor
    Motherboard
    Intel
    Memory
    16GB DDR4 Ram
    Graphics card(s)
    Intel Celeron
    Sound Card
    Realtek HD Audio
    Screen Resolution
    15"
    Hard Drives
    114GB SSD
    Internet Speed
    400mbps
    Browser
    Google Chrome
    Antivirus
    Windows Security
Thank you for your great post

If the more serious contributors in this forum haven't met your criteria for providing a convincing argument, then next logical steps are:
I take that as confirmation.

I was not sure, if the new added information would change all of your answers.

I thought maybe, the new details could change how all of you answered.

Thank you
 

My Computer

System One

  • OS
    Windows 11
    Computer type
    Laptop
The comments along the lines of "I scanned, my AV found nothing, I'm good" always makes me chuckle. If you had a blind security guard watching your house and the criminal was quiet enough would the guard know the bad actor got into your house? The meaning is malware can be very stealthy and employ anti-forensic, evasion and analysis techniques to bypass AV solutions.

I wish I could find the info-graphic that ranks top AV/EDR solutions by bypass/evade difficultly, Defender is near the bottom (mind you this is ranking top enterprise solutions such as Crowdstrike, SentinelOne etc)

I would also beat the point already made many times no AV/EDR is 100% effective which is why security teams in companies never just deploy AV/EDR, but instead deploy many many layers of defenses. Even then security isn't 100% but it becomes increasing difficult for threat actors to get into a network and meet their objectives without being blocked and/or triggering alerts and a CSIRT engaged to clean up the threat/breach

My long winded point is the more DIVERSE controls you have deployed the safer you will be.

If you're ok with just basic malware scanning abilities then Defender is probably fine, if you want more coverage then paid solutions will include additional controls such as

  • In memory scanning (some malware never writes to disk and is harder to detect)
  • Web content filtering (this will reduce the risk of spam and phishing)
  • DNS filtering (help block 2nd, 3rd... Nth stage malware payloads, spam and phishing)
  • Password manager (if you don't already use one) help you have unique passwords per site/application to prevent credential stuffing attacks
 
Last edited:

My Computer

System One

  • OS
    Linux Mint
    Computer type
    Laptop
    Manufacturer/Model
    System76 Lemur Pro
The comments along the lines of "I scanned, my AV found nothing, I'm good" always makes me chuckle. If you had a blind security guard watching your house and the criminal was quiet enough would the guard know the bad actor got into your house? The meaning is malware can be very stealthy and employ anti-forensic, evasion and analysis techniques to bypass AV solutions.

I wish I could find the info-graphic that ranks top AV/EDR solutions by bypass/evade difficultly, Defender is near the bottom (mind you this is ranking top enterprise solutions such as Crowdstrike, SentinelOne etc)

I would also beat the point already made many times no AV/EDR is 100% effective which is why security teams in companies never just deploy AV/EDR, but instead deploy many many layers of defenses. Even then security isn't 100% but it becomes increasing difficult for threat actors to get into a network and meet their objectives without being blocked and/or triggering alerts and a CSIRT engaged to clean up the threat/breach

My long winded point is the more DIVERSE controls you have deployed the safer you will be.

If you're ok with just basic malware scanning abilities then Defender is probably fine, if you want more coverage then paid solutions will include additional controls such as

My concerns are regarding:
Overall malware from the internet
And
Some hacker trying to infect my system via Bluetooth or via the laptops wifi connection

I was looking at this test:

"The test-set used contained 10053 samples collected in the last few weeks."
-
Is it new malware or also old malware the test i made of?

For Defender (Microsoft) - its close to 100% for online functions. I think that is quite good.
But:
"users should be aware that merely being online does not necessarily mean that their product’s cloud service is reachable/working properly."
-
So if the cloud service is not connected, then its only the offline function, and that sits around 63%.
And then you are screwed?

  • In memory scanning (some malware never writes to disk and is harder to detect)
I have read several reports, that Defender does well against fileless malware.

  • DNS filtering (help block 2nd, 3rd... Nth stage malware payloads, spam and phishing)
On the laptop itself, or on the router?

------------------------------------------

But how would my laptop get infected with malware in my scenario?

New laptop
Windows 11 S
Windows S mode on
OOBE
MS Defender or McAfee LiveSafe selected as the antivirus - I believe MS Defender was the selected AV from the start
Internet connection for a couple of minutes during OOBE setup

After completing OOBE
In Windows, internet connection for a couple of minutes, just to turn S mode off
When S mode was turned off - turned off the wifi and internet connection
Did not open any internet browsers
Did not visit any websites
Did not open any emails


14 days later
Turned on wifi and internet connection for a couple of minutes
Download one software from Microsoft Store
Turned off wifi and internet connection again
Did not open any internet browsers
Did not visit any websites
Did not open any emails


Wifi and internet connection has been permanent off since.

The Bluetooth connection was shutdown shortly after completing OOBE.
Wifi connection was only active during above times.

The laptop only connected to the internet through cellular internet sharing with Iphone.
At no time was the laptop connected to a network.

I can't say how much the laptop was online during the factory / manufacturer proces.

Thank you
 

My Computer

System One

  • OS
    Windows 11
    Computer type
    Laptop
There's nothing except the power plug that will keep your system 100% secure.
 

My Computers

System One System Two

  • OS
    Windows 11 Pro 24H2, Build 26100.4351, Experience Pack 1000.26100.107.0
    Computer type
    PC/Desktop
    Manufacturer/Model
    Home Brew
    CPU
    Intel Core i5 14500
    Motherboard
    Gigabyte B760M G P WIFI
    Memory
    64GB DDR4
    Graphics Card(s)
    GeForce RTX 4060
    Sound Card
    Chipset Realtek
    Monitor(s) Displays
    LG 45" Ultragear, Acer 24" 1080p
    Screen Resolution
    5120x1440, 1920x1080
    Hard Drives
    Crucial P310 2TB 2280 PCIe Gen4 3D NAND NVMe M.2 SSD (O/S)
    Silicon Power 2TB US75 Nvme PCIe Gen4 M.2 2280 SSD (backup)
    Crucial BX500 2TB 3D NAND (2nd backup)
    External off-line backup Drives: 2 NVMe 4TB drives in external enclosures
    PSU
    Thermaltake Toughpower GF3 750W
    Case
    LIAN LI LANCOOL 216 E-ATX PC Case
    Cooling
    Lots of fans!
    Keyboard
    Microsoft Comfort Curve 2000
    Mouse
    Logitech G305
    Internet Speed
    Verizon FiOS 1GB
    Browser
    Firefox
    Antivirus
    Malware Bytes & Windows Security
  • Operating System
    Windows 11 Pro 24H2, Build 26100.4351 Experience Pack 1000.26100.107.0
    Computer type
    PC/Desktop
    Manufacturer/Model
    Home Brew
    CPU
    Intel Core i5 14400
    Motherboard
    Gigabyte B760M DS3H AX
    Memory
    32GB DDR5
    Graphics card(s)
    Intel 700 Embedded GPU
    Sound Card
    Realtek Embedded
    Monitor(s) Displays
    27" HP 1080p
    Screen Resolution
    1920x1080
    Hard Drives
    Crucial P310 2TB 2280 PCIe Gen4 eD NAND PCIe SSD
    Samsung EVO 990 2TB NVMe Gen4 SSD
    Samsung 2TB SATA SSD
    PSU
    Thermaltake Smart BM3 650W
    Case
    Okinos Micro ATX Case
    Cooling
    Fans
    Mouse
    Logitech G305
    Keyboard
    Microsoft Comfort Curve 2000
    Internet Speed
    Verizon FiOS 1GB
    Browser
    Firefox
    Antivirus
    Malware Bytes & Windows Security
Give it a rest man. 68 posts and counting. No software will guarantee 100% protection. You need a hat made of aluminium foil. Or aluminum if an American.
 

My Computers

System One System Two

  • OS
    Windows 11 Pro 24H2 26100.4202
    Computer type
    Laptop
    Manufacturer/Model
    Acer Swift SF114-34
    CPU
    Pentium Silver N6000 1.10GHz
    Memory
    4GB
    Screen Resolution
    1920 x 1080
    Hard Drives
    SSD 2TB
    Cooling
    fanless
    Internet Speed
    150 Mbps
    Browser
    Brave
    Antivirus
    Webroot Secure Anywhere
    Other Info
    System 3

    ASUS T100TA Transformer
    Processor Intel Atom Z3740 @ 1.33GHz
    Installed RAM 2.00 GB (1.89 GB usable)
    System type 32-bit operating system, x64-based processor

    Edition Windows 10 Home
    Version 22H2 build 19045.3570
  • Operating System
    Windows 11 Pro 23H2 22631.2506
    Computer type
    Laptop
    Manufacturer/Model
    HP Mini 210-1090NR PC (bought in late 2009!)
    CPU
    Atom N450 1.66GHz
    Memory
    2GB
    Browser
    Brave
    Antivirus
    Webroot
I put a lot more emphasis on my backup scheme, especially off-line backups. If a hacker is determined enough, even the NSA computers aren't 100% secure, so I prefer to make sure I have an easy recovery path in case of any major disaster befalling my computers.
 

My Computers

System One System Two

  • OS
    Windows 11 Pro 24H2, Build 26100.4351, Experience Pack 1000.26100.107.0
    Computer type
    PC/Desktop
    Manufacturer/Model
    Home Brew
    CPU
    Intel Core i5 14500
    Motherboard
    Gigabyte B760M G P WIFI
    Memory
    64GB DDR4
    Graphics Card(s)
    GeForce RTX 4060
    Sound Card
    Chipset Realtek
    Monitor(s) Displays
    LG 45" Ultragear, Acer 24" 1080p
    Screen Resolution
    5120x1440, 1920x1080
    Hard Drives
    Crucial P310 2TB 2280 PCIe Gen4 3D NAND NVMe M.2 SSD (O/S)
    Silicon Power 2TB US75 Nvme PCIe Gen4 M.2 2280 SSD (backup)
    Crucial BX500 2TB 3D NAND (2nd backup)
    External off-line backup Drives: 2 NVMe 4TB drives in external enclosures
    PSU
    Thermaltake Toughpower GF3 750W
    Case
    LIAN LI LANCOOL 216 E-ATX PC Case
    Cooling
    Lots of fans!
    Keyboard
    Microsoft Comfort Curve 2000
    Mouse
    Logitech G305
    Internet Speed
    Verizon FiOS 1GB
    Browser
    Firefox
    Antivirus
    Malware Bytes & Windows Security
  • Operating System
    Windows 11 Pro 24H2, Build 26100.4351 Experience Pack 1000.26100.107.0
    Computer type
    PC/Desktop
    Manufacturer/Model
    Home Brew
    CPU
    Intel Core i5 14400
    Motherboard
    Gigabyte B760M DS3H AX
    Memory
    32GB DDR5
    Graphics card(s)
    Intel 700 Embedded GPU
    Sound Card
    Realtek Embedded
    Monitor(s) Displays
    27" HP 1080p
    Screen Resolution
    1920x1080
    Hard Drives
    Crucial P310 2TB 2280 PCIe Gen4 eD NAND PCIe SSD
    Samsung EVO 990 2TB NVMe Gen4 SSD
    Samsung 2TB SATA SSD
    PSU
    Thermaltake Smart BM3 650W
    Case
    Okinos Micro ATX Case
    Cooling
    Fans
    Mouse
    Logitech G305
    Keyboard
    Microsoft Comfort Curve 2000
    Internet Speed
    Verizon FiOS 1GB
    Browser
    Firefox
    Antivirus
    Malware Bytes & Windows Security
Give it a rest man. 68 posts and counting. You need a hat made of aluminium foil. Or aluminum if an American.
He's a psycho-spammer.
 

My Computer

System One

  • OS
    Windows 11 Pro 23H2
    Computer type
    Laptop
    Manufacturer/Model
    Lenovo IdeaPad L340
    CPU
    Intel Core i3-8145U
    Memory
    16GB
    Hard Drives
    500 GB M2 1 TB HDD
    Internet Speed
    400 MB
    Browser
    Chrome | Edge
    Antivirus
    Microsoft Defender | Block unknown executables | Various ASR rules enabled | Smart App Control
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