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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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
168 views

Secure installation of KVM VPS?

This question has also been asked on Server Fault, but was not taken seriously. I hope this is a better place for it I'm going to install Debian Wheezy on a KVM VPS. VNC access to console is enabled, ...
2
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1answer
208 views

2-Factor Auth with SSH

I recently acquired a Synology NAS (DS1513+). I am looking to expose SSH access remotely and to that end would like to harden SSH as much as possible. Is 2 Factor auth possible and if so what are the ...
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3answers
226 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
44 views

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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1answer
166 views

Do I need logging enabled in my rules in IPFW for sshguard-ipfw to work/blacklist ip's?

From the FreeBSD handbook: Even with the logging facility enabled, IPFW will not generate any rule logging on its own. The firewall administrator decides which rules in the ruleset will be ...
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1answer
1k 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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1answer
512 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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2answers
3k views

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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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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1answer
1k views

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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1answer
185 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 ...
4
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1answer
201 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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1answer
2k views

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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3answers
21k views

Converting keys between openssl and openssh

If I use the following openssl req -x509 -days 365 -newkey rsa:2048 -keyout private.pem -out public.pem -nodes I get private.pem and public.pem If I use ssh-keygen -t rsa -f rsa I get rsa and ...
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2answers
310 views

Recently set up a server, Need security help

I set up a server running debian I opened port 22 allowing access to ssh into the port. I keep getting weird messages in my router log saying: [LAN access from remote] from 211.161.46.101:57201 to ...
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1answer
174 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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2answers
527 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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5answers
6k views

How often should an SSH key pair be changed?

I've been using a 1024-bit RSA key for passwordless SSH between my own systems for years. More recently I've also started using it for passwordless access to my hosting providers and to source code ...
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1answer
2k views

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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1answer
219 views

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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1answer
263 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
410 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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2answers
406 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
921 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
979 views

What's the hash for in ECDHE-RSA-AES-GCM-SHA?

Presumably the SHA is for deriving the AES key from the shared secret. Where else is the hash used? ECDH just does ECC (no hashing). RSA does masking and padding but this doesn't involve the ...
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3answers
208 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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1answer
46 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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2answers
151 views

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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2answers
349 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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1answer
2k views

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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1answer
65 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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1answer
343 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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1answer
45 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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2answers
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Taxonomy of Ciphers/MACs/Kex available in SSH?

SSH offers a large variety of algorithms for Ciphers, MACs and KexAlgorithms configuration options. Sometimes I need quick and light (my own internal network), and sometimes I want all the ...
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2answers
450 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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7answers
17k views

Invalid users trying to log in to my server

I'm seeing a lot of log entries that appear to be failed login attempts from unknown IP addresses. I am using private and public keys to log in with SSH but I have noticed that even with private ...
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1answer
206 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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2answers
441 views

Attacks in SSL and SSH

Assume that we have two end-host A and B connected by two routers R1 and R2. A wants to send a large file to B. A decides to establish SSH connection with host B using public key authentication. ...
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1answer
278 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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2answers
2k 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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2answers
206 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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1answer
179 views

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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1answer
828 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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2answers
210 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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3answers
2k views

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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2answers
6k views

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
55k views

What is the difference between authorized_key and known_host file for SSH?

I am learning basics of SSH protocol. I am confused between the contents of the following 2 files: ~/.ssh/authorized_keys: Holds a list of authorized public keys for servers. When the client ...
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2answers
595 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
439 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 ...