SSH (Secure shell) is a protocol for secure communication between computers to execute remote commands, transfer data and tunnel TCP connections.

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Does restarting an encrypted session increase security and deter attacks?

When a user initiates a SSH connection for example, keys are exchanged and a session is established with a new "passphrase" each time. If an attacker were to attempt to brute force this connection, ...
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662 views

Is mosh now recommended by the security experts? (2014)

Mosh has been around for a while now. Although it's claimed to be "a replacement for SSH" by its authors, mosh does actually depend on ssh to do the initial authentication, after which an instance of ...
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444 views

Convert RSA SSH public key file into x509 certificate

I have a RSA SSH public key which I have converted from a x509 certificate and I want to be able to convert the SSH key back into a x509 certificate to compare the values with the original ...
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Why are DSA keys referred to as DSS keys when used with SSH?

When I generate a DSA key with ssh-keygen -t dsa, the resulting public key will begin with ssh-dss. How come? Why not ssh-dsa?
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Should I publish my public SSH key with user@hostname at the end?

In ~/.ssh/id_rsa.pub my public key is stored as: ssh-rsa magicmagicmagicmagic...magicmagic username@hostname When publishing my public key, should I include the username@hostname bit? Can I ...
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ECDSA vs ECDH vs Ed25519 vs Curve25519

Among the ECC algorithms available in openSSH (ECDH, ECDSA, Ed25519, Curve25519), which offers the best level of security, and (ideally) why?
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Managing and storing lots of SSH keys in the cloud

I have a pool of cloud servers (~50) that need to talk to many other remote cloud servers (~4000) using SSH. Each remote server has its own SSH key, so we need a place to store all of these remote ...
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169 views

Building an VM with Vagrant and connecting with ssh+2FA to protect a bitcoin wallet?

I would like to try to build a Virtualbox image to use with Vagrant. This is the features: Login with SSH + 2FA (Google Auth) No X No internet connection Copy unsigned transaction, sign it and ...
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174 views

Is there a way to split up my SSH Key using Shamir's Secret Sharing?

I have a few servers and machines that I regularly login to, so I was wondering if it was possible to secure them using a version of Shamir's Secret Sharing. I thought if I could split my private key ...
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138 views

how to create an encrypted ssh tunnel between local machine and final machine?

My machine at work is behind a firewall. To connect to it first i need to connect (ssh) on another machine and then through this machine i make the ssh on my machine. In other words, there is a middle ...
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Is sshpass utility insecure than manual ssh password authentication?

I'm planning to automate copying a large file to a remote server over ssh using rsync, using following command : sshpass -p '<PASS>' rsync --partial -av --progress --inplace --rsh='ssh -p 22' ...
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Surfing web anonymously on a mac using Firefox SSH and Tor [duplicate]

I want to download and upload to the internet anonymously. I have successfully configured Forefox to access internet through a secure SSH tunnel service (and remote server). I use 'SSH Tunnel Manager' ...
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377 views

Someone logged on my Centos VM; Can they attack the host OS?

I'm using Windows 7 and decided to learn Linux Administration (Centos 6.4) using Oracle VirtualBox to host the Linux system. In my network configuration I choose "Bridged Adapter". I set the VM's IP ...
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1answer
236 views

How do I find out if I'm connecting to a spoofed server after getting “The authenticity of host [hostname] can't be estabilished”?

I've been SSHing into my VPS for months with no problems and this morning it returned this familiar message: The authenticity of host '[hostname]' can't be established. ECDSA key fingerprint is ...
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2answers
367 views

Is SSH secure and what are the recommended modes of operation?

Given the recent confirmation of weakened and broken encryption schemes and implementations, how does the community feel about the security of SSH? It seems there has been very little discussion ...
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3answers
915 views

Is an SSH session to a mistaken site a security exposure?

A few minutes ago I attempted to ssh to a server I have at my office. Since it is a new server my public key has not been set up there so I had to type my password in manually. After three times of ...
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1answer
7k views

How to harden SSH on CentOS 6.5

I have a new (first time) CentOS 6.5 server being used for a web server. Our security team has identified the following weakness: The SSH server is configured to allow either MD5 or 96-bit MAC ...
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1answer
44 views

“holding open” encrypted home with local ssh

I have a couple of machines that I use for purely automated stuff, with home directories encrypted using ecryptfs. So even if the machine is powered on, those directories aren't decrypted unless that ...
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Do simple Linux servers really need a non-root user for security reasons?

Playing devil's advocate, Let's assume I purchase a Linux server from a hosting provider. I am given a password for the root user and am told I may login using SSH. The only purpose this server has ...
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199 views

What is the safest way to copy a file from an untrusted system?

Scenario: There are two computers running GNU/Linux, U and T. U is untrusted and T is trusted. A non-executable file F (which may however have been infected with malware) resides on U. (For ...
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408 views

PCI DSS 2.0 and ssh keys

I know the real answer to the auditor. We are a smaller company under 40 total employees that is also PCI level 1 compliant. We've always used ssh keys on internal servers. You can't ssh in from the ...
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281 views

How does SSH defend against keystroke-timing attacks?

This paper: https://www.usenix.org/legacy/events/sec01/full_papers/song/song.pdf Explains how SSH can be compromised by analyzing the timing of the keystrokes to guess what the user is typing. It's ...
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Privacy/Security with SSH Tunnels and QuickVPN

I currently use QuickVPN, however, it does not seem to route my web browsing traffic through a tunnel. Am I correct? It only opens up a tunnel for accessing windows shares and documents back at the ...
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What does chacha20-poly1305@openssh.com mean for me?

OpenSSH just introduced a new protocol, chacha20-poly1305@openssh.com, which combines the two algorithms from DJB: ChaCha20 and Poly1305-AES. It was inspired by a similar proposal for TLS, which ...
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63 views

Safe to utilize “unknown” SSH-server? [duplicate]

I've been offered a free Secure Shell at a friends server. However, I was wondering if it might be insecure to join this server from my personal computer at home - may my computer pose any security ...
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259 views

For remotely unlocking LUKS volumes via SSH, how can I verify integrity before sending passphrase?

Although this is closely related to the recently closed question Evil maids in the server room [closed], I believe that it's more answerable. I'd like to unlock LUKS volumes on remotely hosted ...
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43 views

Does having non-ECC SDRAM affect security of the system?

If I don't have SECDED ECC DRAM, is it possible or realistic that a bit could flip around sshd, and grant a lucky lurker access to my system without requiring a valid password?
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445 views

Why should one avoid chains of SSH sessions?

In this document on Security on NSC computing resources, there are several obvious pieces of advice (use a strong password, don't repeat passwords, etc.). One piece of advice I have not seen before, ...
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182 views

Would SSH MitM attacks utilize spoof IPs?

I am presented with SSH log from a SSH server and the said SSH server only accepts connection from 2 known public IPs over WAN. The content of the log shows that a user was successfully ...
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1answer
196 views

Evil maids in the server room [closed]

I am well aware of the fact that physical insecurity in principle means no security. But let´s say I own a root server with full disk encryption which is unlocked/booted via dropbear ssh. In which ...
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1answer
239 views

ISP and ssh tunneling

I have a question about ssh tunneling. Is it possible for the ISP to realize the destination server which I want to connect it via ssh tunneling? I mean the destination website which I want to visit ...
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1k views

What is the difference between SSH and IPsec?

There seems to be similar encryption going into both. They both use asymmetric (RSA, elliptic curves, etc) for the initial key exchange, then go to some symmetric (AES, Blowfish, etc) protocol. I'm ...
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183 views

Securing multiple connections with different protocols all together

I need to secure the communication between an application (runs on any PC and has been designed for Windows) and an external device (runs on UNIX). The application is running on Windows while the ...
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In what ways does increasing SSH host key length increase security

I have read on a few guides on "how to secure SSH servers" that it is a good thing to increase ServerKeyBits from the default of 768 to 2048. Most of these guides seem to be for the entry ...
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Visual fingerprint verification

OpenSSH allows to show a visual representation of fingerprints with the VisualHostKey, see announcement at O'Reilly and here. The output looks approximately like this: # Host github.com found: line ...
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How can I detect if someone is using an ssh tunnel as a proxy to connect to a VPN?

I've got an SSH server setup in a remote location, which I use to tunnel traffic from an android tablet. On the tablet, I have the Cisco AnyConnect app to connect to my company's VPN. We want to be ...
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621 views

Exploiting SUID Binary that connects to SSH server

While conducting a pentest on a Linux machine, I have a limited shell and trying to escalate privileges. One interesting thing that i have found is a binary called connect installed under ...
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195 views

PCI-DSS - key-based shell access to internal servers?

In the following PCI 2.0 requirement, I am not sure how to interpret computer access to internal machines (not remotely accessible): Requirement 8: Assign a unique ID to each person with computer ...
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What's the purpose? Strange login attemps “sshd[***] Received disconnect from **.**.**.**: 11: Bye Bye [preauth]”

I've seen something like: sshd[***]: Invalid user oracle from **.**.**.** // 1st line sshd[***]: input_userauth_request: invalid user oracle [preauth] // 2nd line ...
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3answers
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Is it possible to use a GPG or SSH key for web based authentication in a secure fashion?

Let's say hypothetically I am writing a web application targeting technically inclined, security-conscious users who have no problems generating and using GPG or SSH keys. Is it possible to use said ...
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485 views

SSH Access using private keys

I am trying to practice ethical hacking in my own lab. I have got limited shell in a fedora box in addition I am able to read root files like /etc/shadow trough another vulnerability. Now, I need to ...
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3answers
371 views

Is there an internal equivalent to fail2ban?

fail2ban is a protection against brute-force that locks a user out after a definable maximum failed login-attempts. But if a user already has access to a server with another username already fail2ban ...
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Best way to allow sudo access when using ssh keys

Probably a simple question, but I can't seem to find any actual best practices out there. I manage a handful of servers and I am really getting sick of tracking my passwords in pwsafe. I've been ...
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332 views

Plausibly deniable SSH - does it make sense?

My colleague just told me he can't make outbound SSH connections in his corporate networks, so I advised him to set up a server on 443 port and it worked. I then started thinking that the ...
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Afraid about SSH on my Linux system

I've checked my Linux server (Centos 6) with rkhunter. I found the following in rkhunter log [14:38:54] Checking if SSH protocol v1 is allowed [ Warning ] [14:38:54] Warning: The SSH ...
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220 views

SSH authorized_keys

Can you correct me on this. I create a keypair on my PC. Copy the public key (append to authorized_keys) on the server. Disable password auth on the server, and SSH to server from my PC. I have ...
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Securing WebHosting Shell Access

If I provide SSH access to users who has paid webhosting service, what security measures should be applied ? What I can think of: SSH keys RSA of 4096 size (shall be secure for a while) Apache ...
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How do I get the RSA bit length with the pubkey and openssl?

I have a public key generated with ssh-keygen and I'm just wondering how I get information on the keylength with openssl?
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What effect has MaxAuthTries=1?

I configure a new server right now and ask myself what is the internally effect if I set MaxAuthTries=1 in sshd_config. The server only accept key authentication an no root logins. Has this setting ...
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Securely transferring data from service provider to client

Suppose a client C wants to transfer form a service provider P, who collected data on behave of C using a web-application. Additionally, suppose the amount of data is larger than 100 MByte and ...