Category Archives: firewalls & security

Removing files and folders with secure-delete

Deleting files on Linux is as simple as: rm file_name
Deleting folders is simple as well: rm -r folder_name

Both of these fail from the security standpoint since the content is still present on the hard drive until the blocks that hosted it get overriden with some new data.

To delete files and folders securely there are, at least, two options

  1. Use dd commands. This can go wrong quickly if done incorrectly.
  2. Install secure-delete. On Debian: sudo apt-get install secure-delete

When secure-delete is installed then deletion of file is as simple as:

srm file

For folders:

srm -r folder

The only thing getting added here is the letter s. However, when you are deleting multiple objects be prepared to wait for some time. For example: Getting rid of an old user´s home directory was about 40 minutes of waiting with Ryzen3 3100 machine having an SSD and 8GB of DDR4.

Dual booting Linux and Windows and a static dhcp lease on a hardware firewall

Let’s say that you are using a hardware firewall. It may be Ipfire or Pfsense box or something else. You have a setup, which focuses on security and hence you have given each and every machine a static lease from the firewall’s dhcp server. The previous means that you might have a setup where dhcp range is small and occupied by your machines. Also, since you have given each machine a static lease you also know their local ip addresses and you are also able to tell all the mac addresses of the devices in your network. Continue reading →

Most common security mistakes people do

To be fair, some of these issues are getting quite ancient while some of them are new. The common ground is that they never seem to go away, as there is always some people that keep on doing them. Here is my list of security “horrors” that you or anyone you know should take care of. Continue reading →