The script 'packer/provisioners/post_install.sh' exhibits malicious behavior by performing several harmful actions:
- **Deletes user and root history files**: Uses secure deletion methods to remove history files, potentially to conceal malicious activities.
- **Clears system log files**: Erases log files from '/var/log', hindering the ability to audit and investigate system actions.
- **Disables the root account**: Locks the root account password without ensuring alternative secure administrative access, possibly preventing legitimate administrative operations.
- **Sets a weak default password ('changeme') for the 'admin' user**: Introduces a significant security risk by using an easily guessable password, facilitating unauthorized access.
These actions can be exploited by an attacker to gain unauthorized access, disrupt legitimate operations, and prevent system recovery. The combination of log and history deletion, disabling of root access, and setting weak credentials indicates malicious intent to compromise system security and conceal nefarious activities.