Questions tagged [security]

Content related to computer security., i.e. content about policies, mechanisms, etc. needed make sure data is not leaked or corrupted and services available in all circumstances.

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Is Unix "permission model" conceptually broken?

Suppose a teacher has prepared for his students, before course's beginning, a series of surprise tests that cover it whole. tests ├── subject1 │   └── exam.txt ├── subject2 │   └── exam.txt ├── ...
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How Linux resists single event upsets?

I am collecting information about single event upsets for my report at the university. I found plenty of helpful articles for my theme, but I got stuck with operating systems' resistance against SEU. ...
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Are hidden files in /usr/share/man a security concern?

rkhunter reported that [17:15:45] Checking for hidden files and directories [ Warning ] [17:15:45] Warning: Hidden file found: /etc/.updated: ASCII text [17:15:45] Warning: Hidden file found: /...
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Is a `preloaded library` warning from `rkhunter` a reason to worry?

[17:16:52] Checking for preloaded libraries [ Warning ] [17:16:53] Warning: Found preloaded shared library: /usr/lib/arm-linux-gnueabihf/libarmmem-${PLATFORM}.so ######## #ls /usr/lib/...
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Linux Desktop: How to restrict app's networking, file access and maybe other permissions

This is my first question. Any comments to improve it are highly appreciated. What I am trying to achieve Have a reasonably secure and private (Linux) desktop with at least moderate usability. Where ...
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Password visible while using SCP?

RHEL8 (default bash shell through ssh) > scp source_path remote_host:destination_path & > fg Password: @#$#@#myPassword'sVisibleOhNo!!! First of all, is this just my system, or is it ...
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Implementing DB Security with Linux

I have installed cygwin64 and have been practising linux commands and Shell programming. I am creating a project where I want to restrict file permissions, authenticate user, and execute procedures ...
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Security of /home/.ssh/authorized_keys against spoofing with mount

How is sshd secured against spoofing the home folder with the mount --bind command? I did a test and and mounted the home folder with another folder on a different hard disk. After using the command ...
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What are ways to block a certain user IP address when their data is received from a load balancer and encapsulated in Proxy Protocol V2?

I have a couple of web servers behind an Amazon ELB Network Load Balancer. The load balancer replaces the source IP address of a client packet with it's own source IP address. In example, a client ...
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My custom fail2ban jail fails to load even though fail2ban-regex suggests that it should work?

I've written a custom jail and filter in fail2ban for logging into my service. The log file is located in /var/log/motion/motion.log and a failed login generates a line like this: [0:ml1] [ALR] [STR] [...
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Unexpected behaviour of the "mv" command as non-root user

Recently, I've stumbeld upon this: My non-root user myuser tried to move a file, that belonged to root .. and it worked?!? $ whoami myuser $ ls -lAhd drwx------ 2 myuser myuser 4,0K 4. Nov 14:24 . $...
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How to protect your files from other users?

Fooson and Barson each have a user account on a machine. None of them are administrators. Fooson wants to protect their homefolder so that Barson cannot access the files there. No hard drive ...
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duplicity: how to prevent malicious user from messing with backups

I'm using duplicity on almost every host I'm maintaining for creating backups to a remote location (calling it "backup host"). How often and when to do full or incremental backups depends on ...
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Failed NVMe M.2 SSD, broken filesystem, unwriteable; can I wipe it anyway?

My Samsung 970 EVO M.2 500GB SSD (MZ-V7E500BW) suddenly failed yesterday during a power outage. I now have a warning during POST ("WARNING! Please back up your data and replace your hard disk ...
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Help in interpreting chkrootkit analysis for MS Teams package

I run from time to time a chkrootkit to make sure my install does not get infected. Today I ran it while MS team was on (I need to use it for my classes). Here is what I found: Checking `chkutmp'... ...
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Default ssl_dhparam file used by nginx

Where is the default dhparam file used by the nginx web server after a fresh install of Debian 11? Let's say I do a fresh install of nginx on Debian 11: apt install nginx And I do not have any ...
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Default ssl_dhparam file used by nginx in RHEL/CentOS

Where is the default dhparam file used by the nginx web server after a fresh install of CentOS 8? Let's say I do a fresh install of nginx on CentOS 8: yum install nginx And I do not have any ...
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Ubuntu Advantage: Difference between xenial-infra-security and xenial-infra-updates

Question: When you install Ubuntu Advantage (package ubuntu-advantage-tools) on Xenial, and enable only esm-infra service, it installs the file /etc/apt/sources.list.d/ubuntu-esm-infra.list with the ...
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Coping automatic sites logoff as a user changing linuxes in one PC

What actually cause automatic sites logoff if one single user using the exact same browser (it and its .config is in own partition separately of / OS part) run across linuxes installed in each own ...
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passwd -S Alternate authentication scheme in use

in RHEL 7.9, I do passwd -S on all accounts in /etc/passwd as part of checking user accounts. # passwd -S <account name> root PS 1969-12-30 0 99999 7 -1 (Password set, SHA512 crypt.) bin LK ...
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Custom `PT_INTERP` interpreter results in segmentation fault?

After having read this article on executing arbitrary programs by changing the PT_INTERP to a custom interpreter, I've tried to experiment with this locally: $ cat flag.c #include <stdio.h> int ...
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Some important files (sysctl.conf, ufw, ssh_config, etc.) are 'FAILED' in debsums

I have some packages installed not from the official Debian repositories, so I was looking for something that somehow checks the integrity of the system. The debsums packackage seems to do exactly ...
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Auditd rules to log only user typed commands - without cron etc

I already know how to log all commands from whole system. -a exit,always -F arch=b64 -S execve -a exit,always -F arch=b32 -S execve Now I want to log only commands executed by logged user. Anyone who ...
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Is there any OS that can be installed to encrypt the whole drive that has multiple OS inside?

What am looking for is an OS with or without and interface that can encrypt the whole drive. So when the pc/laptop boots it boots to this os and I have to decrypt the drive and then I should be able ...
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Popup to Prevent Bad USBs [duplicate]

I learned about bad USBs a while ago (Wikipedia Article On bad-usbs). Is there a way that I can get a popup with two buttons ("Use USB", and "Distrust USB" (Don't use it while its ...
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117 views

Debian Bullseye - Disable Console TTY Login for Root

how does one restrict logging into the TTY consoles as 'root' in Debian 11 (bullseye)? In past versions I would empty the contents of /etc/securetty and that would prevent a direct login as 'root' ...
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How do I create a separate XWayland server for each program without a new TTY?

Wayland is a simpler, modern, more secure alternative to the popular X display protocol; however, some programs break under Wayland because they're designed for X. XWayland exists which runs an X ...
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How specifically do userspace programs interact with read-only files/hardware?

In my quest to understand *nix architecture more fully, I came across a situation that I feel probably touches quite a lot of complex topics that I don't quite understand around how programs end up ...
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GPG : no more signatures of a fresh imported key

SHORT GPG doesn't get signatures of an imported public key anymore (with Ubuntu 20.04) while it did it 6 months ago (with Ubuntu 18.04). I don't understand what's wrong. LONG On march, I followed this ...
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Feasibility of storing keys unencrypted on RAM under certain assumptions

We have IoT gateways that run Linux 5.4.31 kernel. These gateways need to manage thousands of devices which are mobile and each has a unique encryption key. The idea is to fetch the key of a device ...
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Firewalld: Error: Invalid_Zone

I got some error I can not solve while setting up a default zone in firewalld. I added the interface with firewall-cmd --zone=public --change-interface=ens3 and then I saw the default public zone ...
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Potential Reach of Windows Malware via Wine and Mono

Scenario: I have a desktop Ubuntu 21.04 system with Wine and Mono installed. The only program I run on Wine is VisiPics, a Windows photo comparison tool. VisiPics needs read-write access to the ...
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Linux OpenJDK Distributions & Best Practices

There are many OpenJDK distributions available (Eclipse Temurin, Oracle OpenJDK, Semeru, etc). As mentioned here, it seems that the IcedTea project is how builds were made available for Debian based ...
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why machinectl/nspawnd conflicts with /etc/securetty.conf

documentation for /etc/securetty.conf only mentions that root login should be restricted on terminal devices not listed there. Login have no problem showing me the login prompt for a regular user on ...
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RFC: ssh -X to run a java app on login via SHELL variable, security and other issues?

I have a java application (not applet) which I run via a script which contains just this: #!/bin/sh /usr/bin/java -classpath /A/B.jar:/X/Y.jar MyApp.Go -p 1 -p 2 -p 3 This app, during initialisation, ...
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How can I enable Samba 1 authentication for a single share?

I'm setting up an old network scanner on a debian machine but it uses smb1 for authentication using ntlm auth = yes under the global settings. I know smb1 it's unsecure so I'm guessing if there's the ...
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Is it possible to cause a interpreter infinite loop?

I'm considering a possible denial of service attack scenario, where a script cause a system resource outage by recursively invoking itself as interpreter. The principle is as follow: The script ...
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Our SIEM show lot of log with src port 80, dest port 22

Yesterday our SIEM system alerted that there are a lot of attempts from one of our VM (which only install nginx and haproxy) connect to a range of external IP addresses (i.e 1.2.3.0/24), which seem to ...
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What permissions should the /boot directory have?

I have been reading a linux security paper that says we should only give root access to /boot directory. What does mean, in terms of permissions, 'only root access to /boot directory'? If I set up my /...
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Password protection for a file for 'write'

My requirement is to to protect a file with password. The user should be able to write/edit the file only after password authentication. But the user should be able to read the file without password ...
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Capture picture after unlocking screen / logging in i3

Running Manjaro with i3wm, and my .i3/config has the following related to locking the screen: # Lock screen exec --no-startup-id xss-lock -- ~/.i3/lock.sh bindsym $mod+Ctrl+l exec --no-startup-id ...
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Ubuntu 20.04.x errors using CIS Ensure loopback traffic is configured UFW security configuration

I’ve only been Linux for about eight months now. I mostly have my head around what’s going on but please when you answer assume I’m far from an expert. I have been attempting to write a lockdown ...
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Predetermined State Computing

I've had this idea of making computing faster or what a friend called a version of Turing computing for a modern day computer. Mainly, the idea is based on utilizing the ECC-RAM utilized nowadays in ...
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Kernel security patches are not needed in Docker containers?

The host and the Docker container use the same kernel, so applying the security patch to the host should be enough, right? Example: the CVE-2021-33909 vunerability: https://ubuntu.com/security/CVE-...
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how to find failed logins from a port or application?

I have a Virtual Machine with CentOS 7 as OS and a database is installed on this server. there are users like dbuser for database administrators . They can login to server via ssh and has complete ...
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Are Arch Community Packages safe from virus or malwares?

I am new on Linux ecosystem and have some confusions regarding the terminology that are being used. With that being said, my reason to switch to a Linux Distro from Windows because it provides a ...
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No keyboard or mouse input until password entered

I'm trying to secure a Pi, and one of the things I'm keen on implementing - if possible - is that whatever input that comes in via the USB ports goes nowhere unless it's a 6-digit password (or longer) ...
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sudo noexec & Lynis

I'm trying to apply ANSSI security recommendations and use at the same time Lynis in order to check the overall hardening level of a Centos-like distro. Following the recommendations, I set the ...
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Firewalld: Services Not Being Added

I tried adding services http, https, smtp, imap, imaps to firewalld but they are not showing when I firewall-cmd --get-services I only see ssh on port 22 which needs to be changed to a different port. ...
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37 views

Can you force a shared object to run as root or use setuid or setgid if its caller is not one of those?

My App needs to have write access to /dev/input/event*. On my Ubuntu system /dev/input/event* is owned by root:input. My app runs fine if I use sudo, but I'm trying to avoid that. So I set my App ...

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