Questions tagged [ubuntu]

Ubuntu is a Linux version derived from Debian. For questions about Ubuntu that are not about security, please post on [AskUbuntu.SE].

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Spawning child processes from root using runuser command

I am working as an intern for an online coding platform startup (similar to LeetCode or HackerRank). The backend is written in Nodejs. Instead of running the code in a sandbox of some sort, the lead ...
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1answer
1k views

Files on external drives executable by default with exFAT or NTFS under Ubuntu

On Ubuntu, if you use (external) drives formatted as exFAT or NTFS, i.e. not ext4 or something made for the UNIX world, you may end up with a situation where all files are executable. This is because ...
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2answers
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Malware techiques via Linux Chrome and its effects, non-root

Is it possible to visit a website with Chrome on Ubuntu and have that site execute shell code on my machine without explicitly downloading anything nor click on some Chrome execute question/popup? If ...
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1answer
997 views

Pivoting with Metasploit

I am trying to exploit a Windows VM on a different subnet behind a dual home Linux VM where I already have a shell. To keep it simple, I have a meterpreter reverse_tcp shell on the Linux VM (192.168....
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1answer
117 views

- Exploit aborted due to failure: not-found: Can't find base64 decode on target

So. I am having some issues at metasploit. I am trying to exploit exploit/multi/http/wp_crop_rce. I am using Docker, in order to install wordpress version: 4.8.9. PHP 7.2.12 (cli) (built: Nov 28 2018 ...
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2answers
3k views

Constant POST request spam to /cgi-bin/ViewLog.asp endpoint

I've got a DigitalOcean server that I use for different temporary servers. Lately I've found that sometimes I get a constant spam of the following requests: POST http://127.0.0.1/cgi-bin/ViewLog.asp ...
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0answers
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Does snapd enforce cryptographic authentication and integrity validation by default for all packages? (debian, ubuntu)

Does the snapd package manager in Debian-based systems require successful cryptographic authentication and integrity validation for all packages? I know that software downloaded with apt-get packages ...
2
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1answer
45 views

Does apt-get enforce cryptographic authentication and integrity validation by default for all packages? (debian, ubuntu)

Does the built-in apt package manager in Debian-based systems require successful cryptographic authentication and integrity validation for all packages? My understanding was that software downloaded ...
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3answers
329 views

Would an Ubuntu server accessible from the internet be hacked within days?

I created an Ubuntu server on Digital Ocean to deploy my app on. Less then 24 hours later, I log in to the server and see this: 18 packages can be updated. 7 updates are security updates. I install ...
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1answer
253 views

Fully-secured screen lock in Ubuntu with encryption

I have Ubuntu 19.10 with full disk encryption. The encryption is effective as long as the system is turned off or restarted. Otherwise the data is unencrypted behind a locked screen which may not be ...
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1answer
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Investigating HP sure start triggering security warnings

The following question belongs more to the HP forums but unfortunately I am not gaining any traction there. Please move the question to another SE if its off topic for this community. Recently I've ...
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0answers
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ARP Spoof dropping ALL connections involved

Please note I have clicked nearly every possible link describing this issue online, and none of them have explained nor assisted in fixing the phenomena. I have a three-computer system, in which one ...
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1answer
177 views

How can I found a source of HTTP request in Wireshark?

There are weird requests to/from the AWS: and another one to/from 177.143.198.104.bc.googleusercontent.com: ( http://whois.domaintools.com/177.143.198.104 ) I use Ubuntu 18.04 Desktop, web browsers ...
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1answer
43 views

Possible to inject in the middle of a ROOT NOPASSWD command with a wild card?

I'm testing for privilege escalations on a Ubuntu 18.04 host, and after running sudo -l , I've discovered a couple of root NOPASSWD commands for a standard user (w/unknown password). These commands ...
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3answers
6k views

Is it possible to exploit a file upload with whitelist and filename hashing?

I have a small web application. Because it is necessary to upload some files I check the file extensions with a whitelist (tgz, jpg, png, pdf, zip, rar, txt, gif, py, c, rb). In addition to that, I ...
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2answers
93 views

is there a way to close 22 ssh port from public, ubuntu?

I am using putty and private key to access my development server. I used Nmap online port scanner, to see which ports are visible to the public, and in fact, the 22 is open. My question is, is it ...
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1answer
892 views

Dirtycow runs (lib-c to root) fine but crashes on reboot

I have ubuntu 14.04.3 server running in a vm with kernel version 3.13.0-83-generic running. I have tested several PoC's gathered here. Most of them crash the kernel (not all the times but sometimes) ...
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Security implications of automatic signing of kernel modules on Debian/Ubuntu (like VirtualBox does)

In the past, to install VirtualBox on Debian/Ubuntu you needed to sign some kernel modules, otherwise it would not work. The process involved creating a key pair, importing the public key as a MOK (...
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2answers
376 views

How to detect malicious files or web shell on a vps web server

How is it possible to detect malicious files or web shell on a vps web server? I used to use a shared hosting, and when I tried to upload any malicious code for testing it got deleted automatically. ...
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0answers
54 views

Intercept HTTP requests for invalid domains in Linux

I am using Ubuntu 18.04. When making a HTTP request to invalid domains, I get a HTML page with javascript code that redirects me to uniregistry a landing page. More specifically, when trying to load ...
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0answers
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Was there ever any malware found in Debian/Ubuntu packages?

With over 50,000 packages in Debian, it doesn't seem too unlikely that some of them may contain malware. On Ubuntu's side, their review process is apparently rather superficial, aimed at catching some ...
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0answers
96 views

Maximum password length for user accounts on Ubuntu

I have a VPS hosted at a remote location. Obviously the host can login directly (without SSH or any keys) on this box and I want to make brute force password guessing as hard as possible for a bad ...
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2answers
192 views

I found an unknown UFW rule on my ubuntu server - have I been compromised?

The server is running the Kubuntu Desktop variant of Ubuntu (I transformed it into a server, I had things configured that would have been a pain to transfer to another installation.). One day I ...
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1answer
116 views

Trojan detected in windows 10 can it affect dual boot Ubuntu

My windows defender detected this trojan: win32/credentialaccess!rfn and I tried to remove it. I use dual boot with Ubuntu: can this also effect ubuntu? If i reset my windows completely can it come ...
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1answer
103 views

Step by step protocol for complete system wipe (suspecting persistent backdoor)

I have reason to believe that there is a persistent backdoor on my device, one which is not removed after a re installation of the OS. I wanted to know the step by step protocol of system wipe to ...
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2answers
28k views

How to get openssl to use a cert without specifying it via -CAfile

I'm using this command: openssl s_client -connect example.com:443 -CAfile /etc/ssl/certs/GTE_CyberTrust_Global_Root.pem It works. If I don't specify that CAfile I get a code 20. The cert is in /etc/...
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1answer
85 views

Check TRIM space on SSD

Is it possible to 'view' the space that TRIM would take care of to see if that space was really wiped? I am using both Windows and Linux.
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0answers
25 views

Does the TPM check the addition/removal of boot-entries

I have an issue that has been puzzling me tegarding the TPM checks on my machine, and I cannot find much documentation about the checks a TPM exactly performs. The issue is the following; I have a ...
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4answers
277 views

Is the Linux / Debian software and package-management ecosystem secure?

My basic question is this: When we are using the Linux / Debian apt-get or yum package system, we're placing a lot of faith in that the packages we're downloading and installing are secure. For that ...
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1answer
47 views

WordPress script injections [duplicate]

I manage an Ubuntu server that runs a number of WordPress sites. This morning one of them went down and was showing the exception PHP Fatal error: Namespace declaration statement has to be the very ...
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5answers
5k views

How do I harden compilers (as suggested by Lynis)?

This article suggests to restrict compilers to root, but does not say how, and I couldn't find anything useful by searching the Web. ii g++ 4:5.3.1-1ubuntu1 ...
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3answers
774 views

How safe is dm-crypt/LUKS? Would TPM make me more secure in this case?

I’ve been looking to purchase a new laptop and I need to have security in mind. I’ve specifically been looking for laptops with discrete or integrated TPM because it’s been my understanding that TPM ...
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2answers
119 views

Unusal GET requests in my nodejs journal - has my nginx/node been hacked? [duplicate]

Saw this in the journalctl for a service I have: jul 29 12:39:05 ubuntu-18 node[796]: GET http://www.123cha.com/ 200 147.463 ms - 8485 jul 29 12:39:10 ubuntu-18 node[796]: GET http://www.rfa.org/...
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1answer
167 views

How to keep backup servers safe?

I use duplicity on a few Ubuntu servers to encrypt backups and send them to a backup server, which then sends another copy to rsync.net, and then, once a week, give it or take, I download these ...
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1answer
51 views

Laravel | Why create a public_html folder and link/move it?

I am using laravel on shared hosting. Under my domain in my folder is the laravel app. Now I see online that many people do weird stuff with the laravel public folder, they either move it to a ...
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5answers
4k views

What are the potential vulnerabilities of allowing non-root users to run apt-get?

There are two ways I can think of doing this: On a system with sudo, by modifying /etc/sudoers. On a system without sudo (such as a Docker environment), by writing a program similar to the below and ...
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2answers
263 views

Encrypt backup files and send them to AWS S3

I have a backup routine via crontab on Ubuntu. This routine generates a compressed tar.gz file and sends it to AWS S3. But I want to encrypt these files and be able to decrypt them when necessary on ...
46
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4answers
14k views

Aren't keyfiles defeating the purpose of encryption?

I just added a drive to my system which is basically a partition mounted for extra storage. I'd like to encrypt it to protect my data in case of god knows what, and by doing that I'd need to enter the ...
1
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1answer
163 views

If someone steals my unencrypted, password protected laptop, would they be able to get into my Google account?

I have a laptop with Ubuntu 20.04 operating system. I am logged into my Chrome browser using my Google account. This means, every time I open my browser, I am already logged into all the Google ...
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0answers
80 views

How to secure an IoT device

Which is the proper way to prevent users to read sensible information stored inside an IoT device (e.g. source code / private keys...)? Fully disk encryption is of course an option, but is it ...
3
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3answers
263 views

Have I been pwned? Public SSH with key

I have a dedicated server with public IP address, opened port 22 and fail2ban running. I am using root account (I know it is wrong but I have to) and I have disabled logins with password. I am using ...
0
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1answer
52 views

Loopholes in secured file server

My system to share private data works like this: I rent a virtual server at a hosting company. There I have a self-signed certificate installed. The folder with the files inside is password ...
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1answer
58 views

VPN as a firewall in a public network

My configuration is: allow only OpenVpn traffic and block any other (income/outcome) traffic with UFW on my ubuntu laptop. unreal scenario: let’s say i have ubuntu with chrome version 50 [2016] on ...
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8answers
4k views

Is a firewall enough of a security measure for an Ubuntu server that hosts a website?

I recently got a VPS with Ubuntu on it, and I'd like to start creating a very basic website. However, I don't know what steps I should take to secure this server. I'm new with Ubuntu, new with ...
0
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1answer
57 views

Are security scrutinies conducted by independent agencies on open source software like Ubuntu or Mozilla Firefox?

Any intentional malware injected into open source software by the same people who are developing them may eventually get known as the source code is open to the public. However, if the code base is ...
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2answers
306 views

How to protect my ubuntu linux computer from screen capture programs or keystroke loggers?

I have a Ubuntu home PC. I often use this system to enter passwords to various websites. Some sites also offer a graphical on screen keyboard to protect from keyloggers. However, I suspect that even ...
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0answers
36 views

Updating Ubuntu [duplicate]

How can I make sure in the terminal that my Ubuntu updates are from the real source? I am asking because I know that one download was fake. It was rkhunter. The update was malware. Done from Bangkok....
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1answer
459 views

dhclient cloud-init /var/tmp process

There's a process that's running that I'm trying to investigate why its running and what its doing. The server is a Linux Ubuntu server running on AWS. Running 16.04. The process in question is: ...
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1answer
95 views

Can a malicious optical disc infect Ubuntu without user action?

Assuming that a malign user has unlimited resources at his/her disposal to infect a computer running Ubuntu, but he/she is only limited in transferring the malware through an optical disc (CD, DVD, BD ...
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1answer
94 views

Maintaining root SSH access on Linux Ubuntu even after losing it? [closed]

Consider I have root ssh access to a Linux server (Ubuntu 18.04 LTS). What is the best way to maintain access even after losing ssh access? Are there any tools out there to help maintaining ...

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