DPI protection is not working in South Korea

[nw2106-alt]

Please answer the following questions for yourself before submitting an issue

• Filters were updated before reproducing an issue
• I checked the knowledge base and found no answer
• I checked to make sure that this issue has not already been filed

AdGuard version

4.12.3

Environment

• OS version: Android 16(One UI 8.5)
• Device: Galaxy S25 FE

HTTPS filtering

• yes, I do

Root access

• yes, I have it

Integration with AdGuard VPN

• yes, I do

Routing mode

Local VPN

Ad Blocking

AdGuard Base filter

Privacy

AdGuard Tracking Protection filter

Social

AdGuard Social Media filter

Annoyances

AdGuard Annoyances filter

Security

No response

Language-specific

List-KR

Other

AdGuard DNS filter

Which DNS server do you use?

Cloudflare DNS

DNS protocol

DNS-over-HTTPS

Custom DNS

No response

What Stealth Mode options do you have enabled?

Protect against DPI

Issue Details

Steps to reproduce:

1. Enable Protect against DPI
2. Connect to any blocked website in South Korea

Expected Behavior

I can go to blocked website

Actual Behavior

I can't go to blocked website

Screenshots

Screenshot 1

Additional Information

No response

[maxikuzmin]

@nw2106-alt Please check the blocked website in the following order:
Try accessing the website via a VPN. Does the problem persist when connected to a VPN?
Does the problem occur when connected to Wi-Fi, mobile data, or both? Please also test using a different mobile carrier or Wi-Fi network.

If possible, please send the AdGuard debug log recorded while attempting to open the problematic website.
In order to troubleshoot this issue, we need to get your application logs.

Here's what we need you to do:

1. Enable debug logging:
   Settings -> General -> Advanced -> Logging level -> Debug.
2. Reproduce the problem, then remember the exact time when it happened.
3. Collect logs:
   Settings -> General -> Advanced -> Export logs and system info.
4. Send this file to qa@adguard.com:
   • include [android] keyword and 6126 in the subject of your email
   • specify the exact time when the issue occurred

[Insight16]

I didn't know this setting even worked. With or without it, websites won't open until you turn on the VPN. At least that's how it works in the country I'm in.

[maxikuzmin]

@Insight16 In most cases, connecting to a VPN server helps you access websites that are blocked in your country.

[maxikuzmin]

@nw2106-alt @Insight16 protect against DPI is designed to bypass certain types of DPI-based filtering, mainly when network equipment identifies and blocks traffic by inspecting TLS/SNI information.

However, not all website restrictions are implemented using DPI. For example, a website may be blocked based on its IP address, CDN infrastructure, geographic restrictions, or other filtering methods that do not rely on inspecting TLS/SNI data.

In such cases, Protect against DPI may not help even though the feature itself is working correctly. This is why a website may still be inaccessible with DPI protection enabled, while it becomes available when using a VPN, since a VPN changes the entire traffic route rather than only modifying how traffic appears to DPI systems.

[maxikuzmin]

@nw2106-alt any news?