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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Are passwordless SSH logins more secure?

I had a long discussion with my co-workers whether key-based SSH authentication (particularly for OpenSSH) is more secure than authentication using passwords. My co-workers always connect to servers ...
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8answers
2k views

What methods are available for securing SSH?

What methods are available for securing SSH?
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3answers
304 views

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). ...
3
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1answer
1k views

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 # ...
3
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1answer
660 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 ...
2
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2answers
961 views

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?
3
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3answers
1k views

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.
2
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1answer
211 views

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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2answers
13k views

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 ...
10
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2answers
1k views

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 ...
1
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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 ...
7
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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 ...
4
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1answer
659 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 ...
3
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3answers
121 views

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 ...
3
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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 ...
9
votes
7answers
3k views

What security implications are there for allowing outbound SSH traffic?

My school currently blocks outbound SSH traffic. Users inside the network cannot use Port 22, and attempting to make an SSH connection over another port is also blocked. (I'm assuming the firewall ...
6
votes
3answers
1k views

What are potential security risks when using an insecure wireless connection?

If someone is using an insecure wireless connection (for example a hot spot in a coffee shop) does it posse a threat even if the person is using a secure application layer protocol? What I mean by ...
2
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0answers
680 views

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 ...
4
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3answers
964 views

In the Diffie-Hellman key exchange, how is the shared base key 'p' known and how are A and B, protected from Eve?

I'm trying to wrap my head around Hellman, Diffie, and Merkle's key exchange design, but after reading the Wiki article about it, I can't figure out how the commonly known factor ('p', I think) comes ...
3
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3answers
7k views

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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3answers
735 views

Encryption-Laws in Iran

According to this article Iran has criminalized the usage of encryption and VPNs. According to this blog post it is still possible to use SSH tunnels in Iran. For me SSH is encryption and thus ...
7
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2answers
2k views

ssh public/private key pair

I am having problems understanding how ssh really works. I know it uses a public key cryptography to encrypt messages. However, I can ssh to a server without first generating a public/private key pair ...
5
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2answers
3k views

How do I get SSH to prompt me with the RSA key instead of the ECDSA key?

I am trying to SSH into my fresh Ubuntu 12.04 server. At the client I have deleted known_hosts. SSH to the host for the first time has it offering me an ECDSA key to verify. The problem is I know ...
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5answers
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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 ...
8
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5answers
867 views

How do RSA fingerprints protect from MITM attacks?

I understand that RSA fingerprints are used to verify that you are really connecting directly to who you want to connect to, and not someone else posing as that site. Like when you do a git push, it ...
5
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2answers
5k views

Creating user specific authentication methods in SSH

I have configured sshd on an Ubuntu server to use key authentication and it is working fine. I had to disable password authentication for key authentication to work. Server is always accessed via ...
3
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4answers
574 views

Can public keys be a security risk when performing password-less SSH logins?

Some companies use monitoring software such as nagios or icinga. In order to perform checks on the servers, they often need password-less SSH logins. The servers being checked put the public key of ...
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2answers
173 views

Do these mysql and ssh issues mean my rails server was hacked?

I'm running a rails application on an ubuntu server on slicehost. I got a pingdom alert that the server was unreachable, so I tried to load the website in my browser. It showed a Passenger error, ...
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6answers
4k views

Is using a public-key for logging in to SSH any better than saving a password?

Using a public/private key pair is fairly convenient for logging in to frequented hosts, but if I'm using a key pair with no password, is that any safer (or less safe) than a password? The security ...
5
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2answers
8k views

Is there an easy way to see a log of SCP activity on a server (ala /var/log/secure for ssh login)?

On Linux systems, /var/log/secure (or similar, depending on distro) shows all SSH login activity. Is there a similar log for SCP? If not, what's a good approach to enabling logging of scp activity ...
4
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2answers
464 views

SSH : Remote Host Identification Changed

As part of my daily routine, I was SSH'ing to one of the corporate servers. However this time I was presented with following message @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ ...
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0answers
54 views

How often should an SSH key pair be changed? [duplicate]

Possible Duplicate: How often should an SSH key pair be changed? I've been using a passphrase-protected 1024-bit RSA key for passwordless SSH via ssh-agent between my own systems for years. ...
12
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2answers
2k views

Security Concerns with X11 Forwarding

What are some of the security concerns and reasons either for or against allowing X11 Forwarding. I have generally taken an approach of not allowing it under the blanket guise of security. Recently, ...
5
votes
4answers
902 views

What's the safest way to access my US-based bank's website from within Mexico? VPN vs SSH vs HTTPS?

I will soon be moving to Mexico and living there for an extended period. During that time I will need to occasionally access my US-based bank's website. I'll always be connecting using my own laptop, ...
1
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1answer
205 views

What would the high priority steps be for securing a small (cloud) application?

No doubt there is much good information at this link on hardening a linux server and at the child links off of that. And at this link to relevant tools it seems there has not yet been a popular ...
0
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1answer
57 views

File directory deletion [closed]

So I heard this guy talkin about how one time he deleted someone's windows directory remotely. He claimed to have gotten into the system and deleted it such that the files are all still there, but the ...
5
votes
1answer
432 views

Protection against a fired IT employee [duplicate]

Possible Duplicate: When a sysadmin leaves what extra precautions need to be taken? We have some servers on two sites. We use Puppet to allow only SSH key (root denied) and authorize users ...
11
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7answers
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Why can an encrypted private key be brute forced?

When using SSH keys to authenticate to a server for remote access, why is it possible to devise the true key and therefore the passphrase from an encrypted private key, without checking each guess of ...
6
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3answers
2k views

Can ssh keyfile security be broken in a few hours if the file is exposed?

At this link there is a claim that if an RSA key has a strong passphrase security might be broken in a few hours if an attacker has the private key. Is there something weak about the security of RSA ...
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3answers
172 views

Smartphone SSH clients with shared user

I am writing an application for smartphones to provide very limited SSH usage. The user cannot perform arbitrary actions when logged in. They can run a specific script(s) only. For various reasons ...
2
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2answers
111 views

Does TLS-OBC only improve security of Web Browsers? Does it improve the security of SSH?

I'm studying the TLS-OBC extension and would like to know if it improves security of non Web-based protocols? Specifically, would it be of any benefit to SSH clients? (version 1 or version 2.x/secsh) ...
4
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3answers
2k views

Is there a compelling reason to ssh tunnel RDP connections?

We don't run any Microsoft products natively in our office, but there are a few folks who use a linux RDP client to access an application on remote virtual desktops with a service provider. Would it ...
9
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2answers
2k views

Is IP spoofing relevant to TCP? Is it relevant for TLS or SSH?

I have read the TCP Connection Establishment on Wikipedia In brief the packets to start are SYN, with a (hopefully) random sequence number A from the client. SYN-ACK, responding, with A+1 and ...
3
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2answers
985 views

Is it less secure to use OpenDNS for banking accounts, SSH, Adsense account?

I have one WiFi connection in my house which I use for my iPad, phone and computers. I want to block adult sites, time consuming sites for every device that use the WiFi connection. So I came across ...
7
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4answers
1k views

can ssh passwordless public key authentication be ok if combined with a VPN?

Having a debate with a coworker about the merits & faults of public key authentication with ssh. I'm basically wondering what all the possible merits and faults are, especially in regards to ...
6
votes
3answers
457 views

Is it OK to use the same password for a Linux login and the SSH private key?

I want to remotely log in to my Linux server with SSH. Public/private key authentication is more secure than password authentication, so I have disabled password-based authentication for SSH on my ...
21
votes
3answers
2k views

What's the common pragmatic strategy for managing key pairs?

I have a small number of different workstations (plus client devices like iPhone) that I use for to connecting to numerous servers using SSH. Originally when I learned about PKI, I created a single ...
4
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1answer
875 views

Security issues related to public keys and SSH

Do I have to mind something specific when using public keys and SSH? Well of course, I have to keep my private key secret (and therefore I should choose a strong pass phrase). But is there something ...
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10answers
10k views

What alternatives are there when SSH is being actively filtered?

Unfortunately our government filters the SSH protocol so now we can't connect to our Linux server. They do the filtering by checking the header of each packet in the network layer (and not by just ...
8
votes
3answers
707 views

Public wifi security protocols

I should apologise first- this post could seem a lot to ask for, but I am starting to go around in circles. I am interested in securing my laptop for when I use public wireless hotspots, as I am a ...