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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What are the risks of SSHing to an untrusted host?

When SSHing to a host that has been compromised (or outright replaced using the stolen server keys) by an attacker with root permissions, what is the worst that can happen to the client? It is well ...
9
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4answers
2k views

How to use public WiFi safely?

The Dangers of Open Wi-Fi How does one go about sending valuable information (for example inputting email username and password) over a free password-less public WiFi network? The only option that I ...
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1answer
227 views

Rsync without ssh access [closed]

There is a host of computers and one of them needs to Rsync a specific folder from each of the other computers. The way its done right now is that this central computer has ssh access to all those ...
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1answer
143 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
879 views

How to use public key in ~/.ssh for asymmetrical encryption with OpenSSL

I want to do an asymmetrical file encryption: openssl genrsa -des3 -out private.key 4096 openssl rsa -in private.key -pubout -out public.key openssl rsautl -encrypt -pubin -inkey public.key -in a ...
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3answers
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How I can prove that SSH attacks are not from my application?

My ruby on rails web application is hosted on Linode. Linode opened a ticket and blamed my Linode server for attacking other servers. The logs revealed that it's a SSH brute force attack which ...
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3answers
204 views

Storing config securely in a semi trusted shared hosting environment

I'm looking for a pattern to store a config file containing sensitive information in a semi trusted hosting environment. Semi trusted in this case meaning I trust them in general, but not with this ...
2
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1answer
751 views

SSH says Authentication tried for XX with correct key but not from a permitted host

I am using and authorized_hosts file to authorise certain keys. One of those is restricted with the prefix from="1.2.3.4", the others are valid from anywhere. When accessing from a machine that has ...
3
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2answers
327 views

any reason not to run tmux/wemux on a bastion host?

Is there any reason to worry about running tmux/wemux on a bastion host? It seems to me that it would open up vectors to have your terminal sessions hijacked by some locally exploited account on the ...
0
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1answer
623 views

Does ssh-keyscan tell you if a server supports RSA or DSA keys?

A question came up on the Unix & Linux SE site: Checking if passwordless ssh authorization is possible without permission for sshd_config?. I immediately thought you could possibly infer this ...
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1answer
143 views

Simple and secure remote installation method that accepts input via a web page?

When installing software on a remote server: Is it possible to let the admin (i.e. the user that installs the software) define admin username and password via a HTML page, in a secure manner? ...
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3answers
219 views

Is it advisable to fully record terminal interaction for incident response?

We are going to be using a jump box to serve as an SSH bridge to our production systems. Assuming that operators are actually logging in to a shell on the jump box and assuming that it is possible to ...
2
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1answer
598 views

What is the actual value of disabling remote root login using ssh?

I have read the answers regarding why you should disable remote root login, but there is something nagging me. Assume this: Scenario 1: Remote server A. Remote root login disabled. Password ...
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3answers
167 views

Working from many places <-> being able to restrict SSH access to server to IP range

I administer a webserver, and while I'd like to restrict the SSH access to an IP range, I wouldn't be able to do so because a) I travel a lot and b) I don't have a static IP at my homeoffice. I've ...
2
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1answer
143 views

SSH Protocol classification version exchange messages

I am trying to classify network protocols over network traffic . Now my task is SSH protocol. I read the RFC and know SSH starts with protocol exchange message from both client and server . Format ...
7
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1answer
199 views

Using / finding covert channels in inter-process communication

I've got a class exercise that involves a virtual game of Werewolves/Mafia. We're not really taught how to do anything in this class, which makes it hard for everyone to do the labs. The idea is that ...
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1answer
1k views

Vulnerability by leaving an open port in a pc

I have the following set-up. Home pc ---reverse ssh tunnel---> to linux server The reverse ssh tunnel is set-up so that on my home pc, port 22 is open, but I have nothing currently listening on that ...
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5answers
4k views

What are the ways to implement two factor authentication?

We have devices that can generate tokens. So we can use tokens with passwords to perform two factor authentication. There are many ways to implement such systems to enhance security. One of two I ...
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1answer
1k views

Two-factor authentication with ssh key authentication and yubikey?

OpenSSH won't invoke PAM at all if public key (RSA) authentication is configured and the client presents a valid key. So if you use key-based auth, you can't enforce 2FA easily. One workaround for ...
5
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2answers
946 views

Linux forensics questions (ssh config, user activity)

I'm a linux noob and have an assignment I'm a bit stumped on... We're given VirtualBox (vdi) images and raw files for the state of a linux server at 3 different dates. We're supposed to answer: ...
10
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3answers
4k views

SSH password vs. key authentication

I've usually been told that public key authentication is strongly preferred over password authentication for SSH. However our previous admin was against public keys and only issued passwords and took ...
3
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3answers
829 views

Using /usr/bin/passwd as login shell

I have a requirement to set up a SSH tunnel between two hosts. SSH server runs on a Linux host, and the SSH client (PuTTY) runs on a Windows host. I have set up a separate user account (say 'tunnel') ...
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4answers
1k views

Brute forcing ssh keys

My problem is a common one: I deleted my SSH key, and forgot to set rm to point to a .trash file. I have the public key, and I need to get in this server. I am not doing this on anyone else's server. ...
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1answer
327 views

Custom Python Server - how to secure it?

I'm going to purchase my own dedicated server service soon and run few python server scripts on it. Firstly, let me tell you that I am total noob when it comes to internet security and was unable to ...
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3answers
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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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1answer
111 views

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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4answers
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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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1answer
2k views

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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1answer
1k views

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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3answers
177 views

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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4answers
712 views

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 ...
9
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1answer
4k views

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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2answers
628 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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2answers
1k views

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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2answers
803 views

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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1answer
4k views

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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4answers
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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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4answers
957 views

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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2answers
3k views

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
187 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
3k views

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 ...
7
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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
209 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
395 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. ...
2
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2answers
188 views

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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3answers
448 views

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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2answers
16k views

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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2answers
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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
758 views

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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4answers
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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 ...