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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GPG warns about unprotected subkeys while using monkeysphere

Issuing monkeysphere subkey-to-shh-agent GPG warns me: gpg: about to export an unprotected subkey then it asks for the passphrase and everything works fine. What's the meaning of "export an ...
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Should I change the default SSH port on linux servers?

Is there any advantage in changing the SSH port, I've seen people do that, but I can't seem to find the reason why. If you have a strong password and/or a certificate, is it useful for anything? ...
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What is the difference between RSA1 & RSA in regards to SSH? Also when is the fingerprint & random art used?

I have searched this site for RSA1 with no results. From multiple google searches I have understood that RSA1 was used in SSH1 (which isn't recommended). However if its a single algorithm why are ...
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Is it secure to transfer an RSA public key by email?

I've set up my VPS'ssh server to accept only key-based identification: I disabled password-based connection. As a consequence I am connecting from home with an RSA key generated prior to password ...
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Make the public key unrecoverable given the private key

OpenSSL seems to bundle the private key together with the public key when it produces .pem files. Is there a way to prevent this from happening; i.e. prevent OpenSSL from creating a .pem private key ...
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Our logs showing a lot of SSH brute force attacks originating on Port 11

this forum has been brilliant so far. Just wondering if I can get a bit more help: Can I get some info on a large amount of SSH brute force attacks originating from port 11 on the external host over ...
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How to set up OpenSSH to use x509 PKI for authentication?

I do not mean simply putting the public RSA key of a x.509 certificate into ~/.ssh/authorized_keys - I'm looking for a way to set up a ssh such that x.509 certificates signed by a pre-defined CA will ...
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655 views

How to secure a truecrypt container allowing access with multiple SSH public keys?

I would like to create a TrueCrypt container which can be accessed by multiple people. The container itself can be stored anywhere, e.g. in a shared folder in Dropbox or Google Drive, ... I would ...
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What are the differences between ssh generated keys(ssh-keygen) and OpenSSL keys (PEM)and what is more secure for ssh remote login?

I have learned there are 2 methods to make SSH remote login easier and secure , those are; ssh generated keys (using ssh-keygen)OpenSSH Keys PEM (.pem) keys usually generated with OpenSSL (Amazon ...
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Is SSH2 still vulnerable to man-in-middle attacks?

With SSH using RSA public key authentication, can an attacker spoof the server IP address and connect with client to obtain client password?
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SSH Bad Protocol Version Identification String- What is it?

I need some help identifying some Bad Protocol version identification errors from our server. I've Googled the strings but not found much about it. We're getting the following: sshd[xxxx]: Bad ...
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SSH: reusing public keys and known-man-in-the-middle

Usually, people recommend to use a single private-public key pair everywhere (if we're not talking about a possibility of compromising the private key): Best Practice: “One per-user ssh key” or ...
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Attract Brute Force SSH Attacks

I posted a question on Server Fault, but got downvoted and had the question closed. One of the comments suggested looking over here, so here goes: For my senior project, I'm working on an ...
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3answers
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how safe is a home NAS with ssh access?

I'm thinking about acquiring a NAS from Synology (or QNap), these are pretty cool NAS and do much more than just storing files. Some extras include: ssh, ftp, telnet, mail servers photo gallery ...
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3answers
197 views

How to regain access to the server?

I have a Debian server with KVM available 24/7. It was recently broken into and its root password changed. My hosting provider has restored my access and helped me change the password. But in the ...
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2answers
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Disabling authentication via DSA keys in OpenSSH?

How can I disable DSA and ECDSA authentication on my server with OpenSSH 5.9? Sifting through the documentation material and doing a web search didn't yield any results - only an old bug report for ...
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1answer
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What are the differences between the arcfour, arcfour128 and arcfour256 ciphers in OpenSSH?

What are the differences between the arcfour, arcfour128 and arcfour256 ciphers in OpenSSH? I am interested about: speed and security implications. I know that arcfour is fast for file transfers, ...
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1answer
216 views

Implementing Secure Remote Password with Remote Desktop Application

I had read the Secure Remote Password Protocol paper written by Tom Wu. This protocol is resistant to dictionary attacks. I have also go through some papers regarding to VNC attacks due to weak ...
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2answers
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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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2answers
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Why CAs instead of global fingerprint database?

Why do we use "too big to fail" CAs and the chain of trust instead of a global fingerprint database in a similar vein to how ssh works?
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Can I develop SSH-based tools within United States?

It is well known that development of open-source cryptographic tools is very problematic within the United States: all open-source ssh-based software was specifically developed outside of the US of A ...
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OpenSSH default/preferred ciphers, hash, etc for SSH2

When using OpenSSH server (sshd) and client (ssh), what are all of the default / program preferred ciphers, hash, etc. (security related) and their default options (such as key length)? So, what are ...
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Which SSH security is stronger? 2 Factor or Public key

For SSH authentication, which is more secure? 2 Factor Authentication using a USB token/Google Authenticator(time based) OR Public/private key with password Or could they be both used at the same ...
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2answers
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length of ciphers versus length of key

ssh-keygen defaults to RSA (for SSH protocol 2) and a 2048 bit key. At this description of ssh The supported ciphers are: 3des-cbc, aes128-cbc, aes192-cbc, aes256-cbc, aes128-ctr, ...
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Brute-force an SSH-login that has only a 4-letter password

Suppose, you know that a certain computer is only protected by such a short password, then you could just try every possible combination easily. How would a script look like, that tries to crack that ...
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4answers
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I think my server is under attack, what can I do to stop it? [duplicate]

Possible Duplicate: Invalid users trying to log in to my server I have a small ssh server mostly used for file sharing. A couple of other people and I use it and there are only 3 users. ...
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Vulnerabilities of Secure Shells

I ssh into my school's engineering computer to submit large programmin projects on a regular basis. Are there any vulnerabilities or worries about using this channel so frequently? What makes a secure ...
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330 views

What are some steps to take for securing a Linux server that aren't in this list of obvious ones?

Obvious things: Disable root login (rather, don't enable it) Secure SSH (no root login, key auth only, timeout after inactivity, whitelist users who can SSH in, etc.) IP Tables firewall whitelisting ...
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235 views

SSH Log: “Accepted password for user…”

I have only port 29999 open for SSH connections. But in the log file I see entries like this: Accepted password for user1 from 190.101.200.100 port 55805 ssh2 saying that a connection was accepted ...
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145 views

Improve SSH logs

I want to improve my SSH log. I would like to basically be able to see failed attempts with ip address and the password used. is that possible? Right now I see something like this: Failed password ...
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3answers
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Petraeus scandal - what would have been a better way to communicate electronically [closed]

Not a security professional here but .... having read through how it happened, it's clear sending these emails from the shared account by Paula Broadwell was the problem (if I understand correctly). ...
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1answer
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How to restrict SSH access outside of LAN? [closed]

We have several dedicated servers. We need to ensure "root" user can not be accessible through SSH outside of LAN. I have searched and found the followings # ...
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1answer
661 views

Replacing weak SSH fingerprint algorithms

Even though MD5 has been broken for years and its vulnerabilities have been used to create real-world rogue X.509 CAs and other horrible things, OpenSSH and PuTTY still use MD5 as the default public ...
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How to correctly secure a ssh session against MITM attack?

How do you improve the security of your ssh session against a man-in-the-middle attack?
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SSH key-type, rsa, dsa, ecdsa, are there easy answers for which to choose when?

As someone who knows little about cryptography, I wonder about the choice I make when creating ssh-keys. ssh-keygen -t type, where type is either of dsa,rsa and ecdsa. Googling can give some ...
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1answer
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Is the `ssh-agent`'s DSA signature deterministic?

In my hopes to use ssh-agent to generate a signature as password I implicitly assumed a deterministic signature. DSA is however supposed to take random value k for signing. However that randomness is ...
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Is piping a `ssh-agent` signed message as a password secure?

There's an encrypted filesystem on a server I ssh into using public key authentication. Since a forwarded ssh-agent can deterministically sign a message (see also the ssh-agent protocol section ...
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How does ssh public key authentication work?

My basic understanding is this: The (connected to) server's sshd uses the public key to encrypt some message The client's ssh or ssh-agent decrypts it and sends something back (the message's ...
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2answers
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Is it okay to widely share the RSA key fingerprint for a host?

When you ssh into a remote box for the first time or if the remote host's key fingerprint has changed (from what's stored in your known_hosts file) you get a warning and you are shown the fingerprint ...
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1answer
560 views

Why does the OpenSSH client on Mac OS X silently launch an ssh-agent for the user?

I'm confused by the difference in behavior of ssh clients I'm seeing on two different hosts. Just to be clear, this is the scenario: "macbox" OS X using OpenSSH_5.2p1 ssh client "sunbox" Solaris 10 ...
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2answers
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Security Concerns with TCP Forwarding

Until now I've been setting TCP Forwarding in ssh always blindly to no but searching on the net, I have trouble finding out what the actual security threat is, when allowing it. The one thing I did ...
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Can the root of a system access to unencrypted data when using a double tunnel?

I connect to a DMZ gateway system (B) which is not secured. From this machine (B) I can connect to the final destination (C). A-->B-->C I created a ssh tunnel from A to B and forwarding the port 22 ...
4
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1answer
660 views

Are SSH packets encrypted even before new keys are sent?

What format does SSH use to exchange (encrypted / plain) packets before new keys are derived? SSH Document says that after key exchange, client and server use negotiated algorithm to encrypt the ...
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1answer
226 views

What dangers are there in storing my private key on different servers?

This question is specifically concerned with storing keys in the cloud, and is somewhat applicable. But I've got a laptop and a desktop computer at home - I'm the admin on both of those systems, and ...
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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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3answers
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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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How to create ssh tunnel using netcat?

I want to create reverse connection between two machines, but these is a firewall in the middle preventing all connections, except ssh. I want to create ssh tunnel using netcat, could you please tell ...
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Hack scenario when a person has a non-superuser shell [closed]

Suppose that there are following three machines in the network: Machine A: Microsoft Server 2003 Service Pack 2 FileZilla 0.9.29 beta ftp server (TCP 21) Mcafee ePolicy server (81), remote desktop ...
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sniff SSH password on the server

Is it possible on the server to log the password encoded by the remote user inside a log. I want to make a honeypot to see the type of user/password used.
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Confusion: Why isn't a passhrase encrypted SSH key two factor auth?

I'm trying to figure out the best practices for accessing my devbox from a public terminal. Most sources I've found recommend protecting the box with some kind of two factor authentication, such as ...