'World's Dirtiest' Forum Hacked by a PDF File

4chan is considered the largest dump on the Internet. Photo: Wired .

4chan is considered one of the most infamous places on the Internet. In existence for more than 20 years, the forum has a monthly active user base of about 20 million, with 200,000 accounts online at any one time. It does not require registration to join.

Due to its anonymity and complete freedom, 4chan is known for hosting a myriad of extreme, controversial, violent, gory, and pornographic posts. The 2014 Hollywood celebrity nude photo leak also originated here.

On the afternoon of April 14, users found themselves unable to access 4chan. That same evening, a user on Soyjak posted a claim of responsibility for the attack. The hacker claimed to have used a PDF file to attack 4chan.

The hackers obtained evidence by publicly releasing 120 GB of sensitive data, including 4chan's source code, administrator information, internal system data, and user IP addresses. They also restored a banned section.

After two weeks of being paralyzed, 4chan confirmed that it had been hacked and restored its system. The "PDF hack" claim was also confirmed. Specifically, 4chan allowed users to download PDFs on many sections. But the system did not check whether the file was actually a document.

Hackers took advantage of this to install malware on 4chan's system and take control, destroying the forum from within. After this incident, 4chan replaced all affected servers, updated the operating system and source code to the latest version. They also temporarily disabled the PDF upload function and will restore it later.

Notably, the Flash section (/f/) has been permanently shut down because the .swf (Flash animation) files also have a similar security vulnerability. 4chan is concerned that they could be exploited in the future.

What surprised many people about this incident was the hacker’s attack method. Most current intrusion procedures rely on social engineering techniques (tricking administrators into giving away passwords). The method used here relies entirely on technical vulnerabilities. This classic method proved effective against 4chan.

After two weeks of being paralyzed, the "Internet's largest dumping ground" is back in business, continuing to be home to some of the most controversial content on the web.

Source: https://znews.vn/dien-dan-ban-thiu-nhat-the-gioi-bi-hack-boi-mot-file-pdf-post1552017.html