Articles

Wed, 10 Jun 2026 10:59:53 +0800

Linux 系统误将 chmod 权限改成了 000，如何恢复?

#include <sys/stat.h>

int main() {
 chmod("/usr/bin/chmod", 0755);
 return 0;
}

ubuntu@ubuntu:~$ which chmod
/usr/bin/chmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/chmod
lrwxrwxrwx 1 root root 8 Sep 27 2025 /usr/bin/chmod -> gnuchmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/gnuchmod
-rwxr-xr-x 1 root root 67K Jan 23 21:34 /usr/bin/gnuchmod
ubuntu@ubuntu:~$ sudo chmod 000 /usr/bin/chmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/chmod
lrwxrwxrwx 1 root root 8 Sep 27 2025 /usr/bin/chmod -> gnuchmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/gnuchmod
---------- 1 root root 67K Jan 23 21:34 /usr/bin/gnuchmod
ubuntu@ubuntu:~$ cat main.c
#include <sys/stat.h>

int main() {
 chmod("/usr/bin/chmod", 0755);
 return 0;
}

ubuntu@ubuntu:~$ gcc ./main.c
ubuntu@ubuntu:~$ sudo ./a.out
ubuntu@ubuntu:~$ ls -lh /usr/bin/chmod
lrwxrwxrwx 1 root root 8 Sep 27 2025 /usr/bin/chmod -> gnuchmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/gnuchmod
-rwxr-xr-x 1 root root 67K Jan 23 21:34 /usr/bin/gnuchmod

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What happens is, they receive the file, read the header that instructs them that it is a compressed file. So they try to decompress the 1MB file to find whatever content they are looking for. But the file expands, and expands, and expands, until they run out of memory and their server crashes. The 1MB file decompresses into a 1GB. This is more than enough to break most bots. However, for those pesky scripts that won’t stop, I serve them the 10MB file. This one decompresses into 10GB and instantly kills the script.

Objective-See: An Open Source Project Org for Apple Privacy and Security

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Objective-See: An Open Source Project Org for Apple Privacy and Security

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LuLu: An open-source macOS network firewall that lets you control each application’s network connections in detail (similar to Hands Off!).

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github.com/siruspen/logrus false
github.com/sirupsen/logrus true

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Articles

Linux 系统误将 chmod 权限改成了 000，如何恢复?

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Linux 系统误将 chmod 权限改成 了 000，如何恢复?

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Linux 系统误将 chmod 权限改成了 000，如何恢复?