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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Limit max connections on port iptables

I want to know how to make a rule for limit the max IPs on certain port because I have a lot of flood with spoofed IPs and when the pool of IPs of my system reaches the limit the system collapses.
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Why does disabling Kernel Page Table Isolation decrease MemTotal?

Iso kernel (Linux 5.4.60), Iso hardware, Iso config apart from case A: CONFIG_PAGE_TABLE_ISOLATION=y and, case B: CONFIG_PAGE_TABLE_ISOLATION=n iomem reports an identical map (apart from Kernel code ...
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Why can't Wine run kernel-mode (ring 0) drivers in a container?

I'm not extremely familiar with systems programming or operating systems, so this is probably a stupid question. But I was trying to get a game running in Wine recently that implements an anti-cheat ...
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Disabling Web camera

My Eee PC comes with a Web cam, which I never use. How can I ensure that it is effectively disabled, so that no software can use it?
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How to delete SSH keys

I am new to this field. I had a server administrator but he left. I assume his key was installed in authorized_keys. How to delete these keys if they exist. How can I find out if they are really (...
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No root, other user privileges?

I know for security reasons I should not use root, my question is if i create a new user what privileges it should get ?
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Why does Message+ randomly pop up on my processes on Kali?

I watch my network using "top" and I notice message+ keeps randomly popping up for about 1-2 seconds then disappears. What is this and why is this happening? I can't find anything on it.
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Why do Linux people apparently hate security? [closed]

Having spent years now trying to get encryption on my headless Raspberry Pi (Raspberry Pi OS installed), that's the only conclusion I can draw. On Windows, all you need to do is install VeraCrypt and ...
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1answer
22 views

grub password protection necessary or overkill in an encrypted system?

I run debian with full encryption and wonder why I would also need a password protection for the bootloader...
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1answer
403 views

Permission denied, but why?

I am trying to back up the contents of my network hard drive called WD mybook live. It Internally, it is running Debian Squeezy on PPC. There are several users on this network hard drive: tony, user2, ...
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1answer
35 views

Logging SSH commands on Linux - is custom kernel the only way?

I've done some research and it looks like that the way linux keeps history is less about security and audit and more about helping the user. Even after making changes to instantly log the command and ...
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History file - logging user and src ip

Is there a way to log the src ip and the user that executed the command to the history file? So far I've not found a way to make HISTTIMEFORMAT log that information
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1answer
47 views

For a directory file descriptor dfd, can I prevent traversing up as in openat(dfd, “..”, …)?

I have a user $service with a directory /srv/$service/subdir. /srv/$service has a mode of 0700, i.e. it's only accessible by $service. That user can open a directory file descriptor to …/subdir or any ...
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903 views

How is the authenticity of Debian packages guaranteed?

What security systems and processes are in place to prevent malicious third parties from hacking/compromising the security of code in the Debian mirrors, or to verify that the packages we get are in ...
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Is there anything wrong with giving ssh users filesystem access?

I am preparing a standalone server which will host several users that are able to log in with ssh public key authentication. They should be able to use the SSH connection to browse a shared folder ...
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Anonymous email client

I want to config any internet activities of the email client being routed by TOR or other proxy, and like TBB, each tab has different IP than others. Or as easy I want, where to download anonymous ...
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1answer
345 views

Was my Unix server compromised?

Someone asked if this constituted a break-in and wondered if their server had been compromised. Jan 12 04:16:51 foo sshd[26725]: Failed password for root from 61.174.51.207 port 1076 ssh2 Jan 12 04:16:...
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Cannot get Ubuntu Live Boot with Grub2 and secure boot with own key material to work

Okay, whats the story here? I've compiled the open source UEFI implementation for virtualization with KVM, aka. OVMF. To make this project interesting I am compiling it with the secure boot feature ...
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1k views

fprint doesn't find my laptop's fingerprint device but lsusb does?

So when i use lsusb i can find the fingerprint device, the name of it is Generic goodix fingerprint device and my laptop is lenovo thinkpad 530s considering that lsusb can find it then why can't ...
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1answer
3k views

Temporarily deny all incoming trafic with firewalld

I'm searching for an equivalent to ufw default deny for firewalld; the idea is that after I log in through SSH to my fresh server, I want to block all incoming new connections so that I have time to ...
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1answer
1k views

How come I can login to another person's session over vnc just by changing the port number?

I have a user account on a server administered by someone else. I don't have root access. The server is CentOS 7. I couldn't connect over vnc on the usual port I use, so I ssh'd into the server and ...
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1answer
4k views

Generate HMAC in Bash without revealing the secret

I'd like to compute a HMAC-SHA512 digest in my bash script. So far I've found only this repeated many times over many different sites. echo -n message | openssl dgst -sha256 -hmac secret -binary >...
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6answers
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UFW: Allow traffic only from a domain with dynamic IP address

I run a VPS which I would like to secure using UFW, allowing connections only to port 80. However, in order to be able to administer it remotely, I need to keep port 22 open and make it reachable from ...
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lastb output empty even after 3 failed login (su) attempts

On one terminal root@Andromeda:~# lastb btmp begins Sat Mar 2 10:03:44 2019 On another one: $ sudo su - [sudo] password for pkaramol: Sorry, try again. [sudo] password for pkaramol: Sorry, try ...
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Server being attacked with key exchange attempts. Not being added to ban list by fail2ban

Looking through the sshd logs, there is a remote machine which appears to be attacking my server. here is an example of an entry. It is always the same IP. May 8 17:57:32 [removed] sshd[99267]: ...
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3answers
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Is having docker installed a massive security hole?

Suppose I have an Ubuntu machine and did sudo apt install docker.io. Did I just put a huge security hole in my machine that will allow anyone with terminal access to escalate into root? I ask that ...
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Psad isn't triggering the script

I can't get the the psad to trigger a script upon scan detection. this is in my psad config; ENABLE_EXT_SCRIPT_EXEC Y; EXTERNAL_SCRIPT /scripts/tomylog.sh --ip SRCIP -v; this script ...
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2answers
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How to verify a public(facebook's) key ? and then sign and trust them

Recently I enabled gpp emails option in facebook. Then they sent me a test mail to check whether I'm able to decrypt that or not. So first I downloaded there public key from Here and imported in my ...
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1answer
325 views

pam_tally2 add an extra failed login

I am trying to use pam_tally2 in /etc/pam.d galaxy I change sshd to the following content #%PAM-1.0 auth required pam_securetty.so auth required pam_tally2.so deny=3 unlock_time=...
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Setup AIDE monitor and hashes are already mismatched

I’m setting up AIDE monitoring on Raspbian. I first tried over ssh but it timed out due to my timeout settings. Then I setup the new AIDE db directly on the RPi command line. I had to overwrite the DB ...
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How to use Linux keyring to create a session-less key that is accessible from cron and services and lives forever until the next reboot?

I would like to create a keyring key that can be used from session-less processes (cron, daemons etc.). Keyctl documentation suggests: keyctl_get_persistent() gets the persistent keyring for the ...
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25 views

How to cache systemd-ask-password data for automatic systemd service restarts?

I have created a web service that requires a password to decipher its config data. The password could not be stored as raw data anywhere on the disk (very strict bureaucratic requirements from the ...
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When you have to use previous or older kernel due to compatibility or dependencies, how long is it safe to use them?

I'm sure a bunch of people are having this issue now. I upgraded Fedora kernel with a magic button in "Software" app and Virtual Box vboxdrv isn't available yet for 5.8 . (Before this last ...
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1answer
34 views

Correct way to verify PGP signature in BASH script (pinning exact long fingerprint)

I have: A file A detached PGP signature of that file in ASCII armor format and A 40-character (long-format) fingerprint identifying the one key that must have a valid signature What is the correct ...
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1answer
39 views

Delete only private signing key from within gpg (without reimporting subkeys or 'rm ~/.gnupg/private-keys-v1.d/KEYGRIP.key')

From what I understand it is considered to be good practice to generate a private-public keypair, generate a subkey for encrypting, export all three keys and store/backup them (e.g. using 'paperkey') ...
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20k views

How to determine if computer has TPM (Trusted Platform Module) available

Wanting to play around with Trusted Platform Module stuff, I installed TrouSerS and tried to start tcsd, but I got this error: TCSD TDDL ERROR: Could not find a device to open! However, my kernel ...
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eToken not detected

I want to use an Aladdin eToken Pro 32k 4.2B on Fedora 32 but it is not detected. It shows as another model in lsusb: Bus 003 Device 009: ID 0529:0600 Aladdin Knowledge Systems eToken Pro 64k (4.2) ...
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1answer
272 views

Why does Linux need SELinux

What is SELinux and what are the advantages of using it? Why does Linux need another layer of protection?
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38 views

Problems with aircrack-ng, ALFA usb not working/causing internet to shut down?

I apologise if this is basic troubleshooting. I bought a AWUS036NEH, which is recognised and properly appearing in Device Manager in Windows 10. I am using Debian 10x 64 bit, on Windows 10 via VMWare ...
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2answers
141 views

Overwrite deleted file

I have deleted a file on a FAT16-formatted flash drive with rm. I can see that the file is still recoverable using testdisk or fls. Is there a way to securely delete the (already deleted) file, ...
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2answers
89 views

Security implications of running user-writable scripts with sudo

I need to run a few commands with sudo. These commands are located either in .bashrc or ~/bin, and stored in a git repository (i.e. dotfiles). I've placed symbolic links in ~root pointing to my user'...
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3answers
25k views

Security implications of forgetting to quote a variable in bash/POSIX shells

If you've been following unix.stackexchange.com for a while, you should hopefully know by now that leaving a variable unquoted in list context (as in echo $var) in Bourne/POSIX shells (zsh being the ...
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1answer
310 views

'pass': Easiest way to synchronize the password-store between multiple machines

I moved to the pass password manager and I'm trying to integrate it as well as possible into my workflow. However, I'm not familiar with deeper synchronization/version-control concepts (git, password ...
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1answer
876 views

Firefox Apparmor Profile

I'm running Ubuntu Mate 19.04. I want to enable apparmor for Firefox. I found an existing profile in /etc/apparmor.d/usr.bin.firefox, which I enabled by deleting /etc/apparmor.d/disable/usr.bin....
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2answers
342 views

How to gradually encrypt the tshark output file along the capture?

In order to secure a packet capture, which method would you use to make all (or close to all) past captured packet utterly unaccessible unless a given password is given. My habbits are to mount an ...
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8answers
11k views

When does the Puppy linux security model make sense?

I have just spent a few hours playing with Puppy linux, which has some very nice features, but there are some things about its approach to security (at least the default settings) that worry me: It ...
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38 views

Backup a LUKS encrypted device on the cloud

I am going to use LUKS for encryption, however I cannot find a thoughtful manual and best practices how to do so. Here I will list my questions, sorry for naivety. Apparently I don't need to encrypt ...
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3answers
4k views

Why does kdeconnect listen on port 1716/tcp all the time? How to close the port / secure it?

Zenmap shows me that port 1716/tcp is open and sudo fuser -v 1716/tcp tells me kdeconnectd is responsible for it. Why does kdeconnectd have the 1716 port opened all the time? And what would be best ...
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1answer
1k views

How to login with both password and fingerprint?

How to configure PAM to require both password and fingerprint to log in? I can do a password / fingerprint login but not both by changing /etc/pam.d/common-auth For password only auth [success=...
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1answer
34 views

Can security modules completely override Linux Kernel's access model?

I am aware of Apparmor and specifically how it can be used to limit a program's access rights where of the file-system permissions otherwise allow. What I'm less clear on is whether it's possible for ...

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