Questions tagged [linux]

Securing Linux systems and applications; understanding Linux security features.

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Almost unattended generation of "a pretty good keypair"

I need to generate quite a lot of gpg-keys for different tasks on my Debian Bullseye (Stable) machine. Also I want the highest level of security while being able to automate as much as possible. ...
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How to only allow whitelisted processes to access a certain file using SElinux?

Let's say you have a important file/folder, and want to only allow certain processes (based on process name, or its corresponding ELF file on the disk, or the digital signature of the corresponding ...
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Can SMB/CIFS credentials be extracted from Linux?

On a penetration test, I have completely compromised a Linux machine and I am now trying to move around the network. The Linux machine has a mounted CIFS share, and I want to get the password used to ...
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120 views

Is WSL 2 secure for commercial work?

Windows Subsystem for Linux (version 2) is getting more and more traction lately with new features being added such as GUI mode over Wayland (WSLg). It seems to me Microsoft really pushes for WSL ...
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1k views

Where are the symmetric keys stored?

I don't seem to find the option to save symmetric keys. What I want to do is that I simply want to encrypt a file and transfer the file and the symmetric key (which is encrypted with the recipients ...
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2answers
204 views

How to completely restrict Steam in Linux to defend against remote zero day exploits?

My question is, how can i completely restrict Steam's processes and modules to only have access to what they suppose to, and not be able to do anything malicious, for example running bin/sh or ...
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56 views

How to do a post-mortem after being hacked [closed]

I am wondering what the general steps are in retrospect for trying to find out how one ends up being hacked. A couple of times I have had Linux servers that ended up being hacked. I noticed this in ...
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1answer
83 views

Utilising 3rd-party AV definitions with ClamAV engine

I have ClamAV/engine pretty widely deployed on most of my Linux/UNIX/POSIX & other boxes - including gateways & at-rest storage, but I've found the ClamAV definitions... lacking... sometimes. ...
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Detect if TLS version prior 1.2 has been disabled on RHEL 7 [migrated]

Situation: I have a RHEL 7 Virtual Machine and I have installed ActiveMQ (v5.16.0) on it (in /opt/...) Since few days some of my clients cannot connect anymore on the openwire SSL port (61617) with ...
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Can you create a fake (malicious) Ubuntu iso

Recently I got into an exchange with someone on social media about the security of Linux versus OSX and Windows. I stated that it is possible (and probable) that someone could code a low level back ...
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1answer
118 views

Why Vulnerability Scanners Ignore Shared Libraries?

First of all, I am new to vulnerability scanning and don't have an experience working with any tooling outside of container specific. So, I don't know if it is a normal behavior for scanners. Please ...
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1answer
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Exploting a Stack Buffer Overflow vulnerability to get privilege access to system

I am trying to complete a buffer overflow challenge. The code I am trying to exploit is below. I can only use the command line in a Linux environment. I understand that writing more than 100 ...
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If browsing the web with root is dangerous, isn't browsing the web with a sudo enabled account only marginally safer?

If I get hit with malware while performing daily tasks (e.g. - checking email, web browsing, etc.) with a root shell, the malware will own my machine. If the aforementioned occurs whilst on a standard ...
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How `sudo` command checks password?

To check the sudo password, we need root permission to even read the /etc/shadow file. But how sudo checks password?
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Does dnf enforce cryptographic authentication and integrity validation by default for all packages? (fedora linux)

Does the built-in dnf package manager in Fedora-based systems require successful cryptographic authentication and integrity validation for all packages? I know that software downloaded with apt-get ...
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Does pacman enforce cryptographic authentication and integrity validation by default for all packages? (arch linux)

Does the built-in pacman package manager in Arch-based systems require successful cryptographic authentication and integrity validation for all packages? I know that software downloaded with apt-get ...
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Is there any point in using an antivirus on Linux? [duplicate]

Root privilege is already a requirement in order to be able to run commands that may impact your system. But, lately, there seems to be surge in malware (e.g. ransomware etc.) that isn't limited to ...
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How does Sequoia allow unprivileged users to get root if it requires mounting a filesystem?

CVE-2021-33909 AKA "Sequoia" is a vulnerability against the filesystem code within the Linux kernel. According to the description of the vulnerability from Qualys Successful exploitation of ...
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What OS do I focus on when learning Cyber Defense?

After some time in the Cyber Defense field, I am noticing that there are different learning paths to take depending on the OS you choose (for example you can learn how to use PowerShelll and lots of ...
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What is a good common approach for encrypted backup/restore on an embedded device?

An embedded device with Linux supports backup/restore of files encrypted with openssl. The idea of backup is: tar -c .... | openssl smime -encrypt -binary -aes-256-cbc -out backupfile.encrypted -...
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Is Linux really not spying on us?

When I ask someone about Linux, people always say it's really safe and this OS doesn't collect your data and these are not spy operating systems. When I ask them "how?" they say, "...
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78 views

Where to store passwords needed by linux processes?

I am working with C++ processes on a linux (CentOS 8) environment. These processes should be able to access an encrypted file on the system. Where should I store the password for this encrypted file? ...
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60 views

Changing password on LUKS2 and SSD

Let's say I have password "password" for my drive using LUKS2. And then I change it to something really unguessable. The slot with password is overwritten. But, on SSD it is not really ...
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130 views

Secure way to run a linux binary which needs access to ressources only available to root?

As a developer, I ask how to approach security concerns regarding permissions of a binary which needs access to resources only available to root users. For example, let's think of a simple tool which ...
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2answers
288 views

What is the point of storing hashed passwords? If that file is read, doesn't that mean the computer has already been compromised?

Why is it necessary to store operating system passwords hashed? From what I've learned, passwords are stored on the hard drive/SSD in /etc/shadow. However, if a malicious agent was able to get access ...
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109 views

What are the disadvantage of only encrypting the HDD compared to FDE with secure boot

I read How secure are most FDE implementations? What are the disadvantage of only encrypting the HDD compared to FDE with secure boot. If I encrypt a disk in a running server, and someone gain access ...
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Is it possible to get malware using cat command? [duplicate]

I want to know is it possible to get malware using cat command from some text files like printf '\033[H\033[2J\033[3J' > file.txt?
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1answer
246 views

Using Hardware Encryption on NVME SSD used as the boot device

I have a question relating to implementing encryption of data at rest. This is possibly more suited to another stackexchange site, so please let me know where would be better to post if I'm a little ...
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3answers
224 views

Identifying a BadUSB using Linux

Using Linux, is there anyway to detect that an arbitrary USB device is a BadUSB or not? For example: Booting a Linux into multi-user.target. No graphical interface / tty (getty login). Plug the USB ...
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194 views

How does having a password hash speed up cracking vs not having a hash (on-site)?

On Windows, user password hashes are not salted and, on Linux, user password hashes are stored in the same root-owned file as the salt. Given this, in what ways might a bruteforce attack to find the ...
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1answer
108 views

Adding a self-signed client certificate to HAProxy for mutual-tls?

I added the client cert into ca.pem as in bind 0.0.0.0:443 ssl crt /etc/ssl/private/asdf.hdavid.io.pem verify optional ca-file /etc/ssl/certs/ca.pem http-request set-header X-SSL-Client-Verify %...
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1answer
68 views

SUID Priv Escalation - LD_LIBRARY_PATH versus ldconfig and /etc/ld.so.conf

Background Currently doing some vulnservers on Offensive Security's Proving Grounds Practice Labs. A vulnserver is a machine configured with vulnerabilities for testing/audit and research purposes. I ...
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How to encrypt and hide a GNU/Linux operating system and create a decoy system?

My goal is to be protected against key disclosure laws and possible extortion. I know dm-crypt can be used to perform full disk encryption for GNU/Linux distros. However, it is not enough. I want to ...
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84 views

Is it insecure for the user to know the process id of a background script on my web server?

I was experiencing an issue on one of my webpages, where an AJAX call is made to another script on the server to generate some files for download. Depending on things like server load, number of files ...
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1answer
146 views

How good/bad are these transparent Linux consumer FDE setup options? (e.g. for auto-unlocking LUKS)

UPDATED Summary: I'm looking at Linux FDE options that are transparent to the user (my parents) in that the user doesn't need to enter 2 passwords. I found/thought of several options and tried to ...
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Is LUKS still an effective option for consumer FDE considering Elcomsoft can break it?

I use Fedora Linux and was recently looking into doing Full Disk Encryption on data drives such as /home on some of my / my family's PCs. I understand that LUKS security will be partially dependent on ...
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1answer
46 views

When changing a PGP passphrase, does it only affect the same key on the other machine?

If I change the password of my PGP key (I use it to sign Git commit) on Computer A, does it affect the same PGP key that I have on the Computer B? Will I still be able to use the PGP key on Computer B ...
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1answer
211 views

How should GNU/Linux noobs harden their dekstop OS?

I'm interested in using GNU/Linux for different reasons. Partly for freedom, privacy, and security. But also to force myself to learn Linux. One issue I’ve found is that desktop Linux seems to have ...
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2answers
172 views

Haven't updated my Windows 10 for more than a year

Almost a year ago, I dual-booted Windows 10 and Linux Mint. And since then, I haven't booted into my Windows 10 OS. I still remember that the Wi-Fi adapter was off when I shut my Windows 10 down. Now, ...
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33 views

bluetooth link encrytion under bluetooth 4 .2 and 5.x

This is a follow up question regarding this answer In Linux does the encryption of the bluetooth link using bluetooth 4.2 or 5.x depend on the version of the kernel - and whether or not the kernel ...
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1answer
60 views

Is there an effective way to disable root access on linux in an office setting

I'm currently working for SaaS a company and as part of a security audit we were advised to remove all administrative access from all laptops/end-user pc's for a Principle of Least Permissions. Is ...
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81 views

Why does the CIS benchmark consider the presence of passwd- a (high) risk [closed]

I've just seen a "high-risk security alert" for the presence of /etc/passwd- (note the trailing '-') on RHEL 8 servers, and don't understand the issue. Apparently the issue originates with ...
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0answers
158 views

How to harden portable Tor Browser installation (SELinux, sandbox)?

tldr How can I define a SELinux policy, that limits filesystem access of portable Tor Browser to its installation directory, say /home/user/.local/opt/tor-browser_en-US? How might Tor Browser be ...
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1answer
95 views

Which remote desktop protocol offers the smallest attack surface? [closed]

I am trying to "outsource" potentially dangerous applications such as web browsing to a separate Linux machine sitting in its own network segment and which is isolated by a rigorous network ...
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2answers
92 views

How to secure containerized python source code deployed at client side cloud

How can we secure a source code which is deployed at client side cloud and is difficult to reverse engineer just like a licensed product The major difference is that I have a service to protect and do ...
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1answer
80 views

How to detect fileless kernel compromise in linux

Is there a way to detect fileless kernel compromise in Linux? The only one way to analyze this kind of attack is by volatility. Volatility is a very good product, but not often updated especially with ...
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84 views

Dynamic port forwarding without sudo or SSH

I have compromised box A and another target server. I don't have SSH on A and want to do port forwarding with escalating to root. I can't install or run services without root, and only have nc and ...
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258 views

How did ntpd get patched to prevent NTP time synchronization attacks?

I recently tested the NTP Time Synchronization Attack as described and demonstrated by Jose Selvi in 2015. Basically, the attack was mostly used to send the victim's clock in the future, so the ...
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1answer
74 views

Changing Linux system files by malware from another OS. Is it possible?

Is it possible to infect important Linux system files with a malware from another operating system? For example, you are using Windows, you have a disk with the Debian operating system connected. You &...
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2answers
81 views

Can a meltdown attack also violate data integrity of other processes or is it just violating data secrecy?

Can a meltdown attack also violate data integrity of other processes by obtaining different passwords or is it just violating data secrecy by reading data it is unauthorized to do?

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