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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6
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173 views

Distinguishing SSH and HTTPS traffic

Alice is an employee of Chris, and Chris does heavy traffic monitoring via its company proxy. Alice wishes to use a Bob's web service while preserving privacy and confidentiality. She has full ...
2
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4answers
4k 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 ...
3
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4answers
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.
11
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4answers
5k 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 ...
0
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0answers
36 views

Silent security on android

I saw a DEFCON talk about owning back a stolen PC/Mac, with a SSHd daemon and a dynamic-ip service installed,running in background. I was wondering if is it possible to achieve tha same results on an ...
9
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1answer
229 views

Yubikeys & SSH - which option is best for lockdown?

My company has a few dozen servers hosted on a cloud provider. All but one (OpenVPN host) is closed to the internet. We're using OpenVPN AS which uses certs + Google Authenticator for login. We are ...
5
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0answers
27 views

Authentication Agent Protocols for SSH

Is the protocol described at https://tools.ietf.org/html/draft-ietf-secsh-agent-02 actually implemented by any ssh agent? pageant implements a different protocol as does OpenSSH's ssh-agent.
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2answers
65 views

What is the safest way to ssh to a machine behind a router?

I am thinking about forwarding port 22, to 22 on the machine behind router, but is it safe? Anyone can try to connect to my public IP on port 22 and then indefinitely try to guess user and password. ...
0
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1answer
78 views

SSH scan against D-Link routers: is there a (new) exploit?

TL;DR if you have a D-Link router perhaps it wouldn't be a bad idea to check its SSH settings and/or username/passwords. I am a long-time user of fail2ban on several machines, almost all Ubuntu 12 ...
0
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2answers
182 views

Does public key auth in SSH prevent most MITM attacks?

I found this article that claims asymmetric crypto signature of DH-obtained key prevents MITM: http://www.gremwell.com/ssh-mitm-public-key-authentication Key idea: The value of 'signature' is a ...
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0answers
14 views

sshd_config file configuration [migrated]

# HostKey for protocol version 1 #HostKey /etc/ssh/ssh_host_key # HostKeys for protocol version 2 #HostKey /etc/ssh/ssh_host_rsa_key #HostKey /etc/ssh/ssh_host_dsa_key #HostKey ...
2
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1answer
33 views

What's the importance of sshd's setting RekeyLimit?

man sshd_config page states: RekeyLimit Specifies the maximum amount of data that may be transmitted before the session key is renegotiated, optionally followed a maximum amount of time ...
3
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1answer
111 views

Is it possible to retrieve SSH v2 credentials in a username/password authentication scheme?

I'm currently analysing a compromised network(root access has been gained to a workstation and logs show that it has been used for port scanning and service brute forcing attacks on the remaining ...
0
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1answer
28 views

How is protected connection between the client and the server carried out when using cloud storage?

How is protected connection between the client and the server carried out when using cloud storage? Based on use of VPN connections or protected protocols at various levels (SSH, TLS/SSL, IPSec)? But ...
14
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2answers
16k views

How is OpenSSL related to OpenSSH?

Is OpenSSH using OpenSSL to encrypt traffic? Or something else?
1
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2answers
141 views

What to do about ssh breakin attempts [duplicate]

Our system used to get bombarded by bots trying to login to the ssh client on the standard port. After switching to another port number the failed login attempts basically stopped completely. ...
1
vote
1answer
23 views

Automated tools to manage or monitor authorized_keys? [closed]

In short Are there any tools that can be used to work with authorized_keys to scan the keys and maintain a database of which servers have which keys? More context I'm a big fan of public key ...
1
vote
1answer
403 views

Digital Ocean “Droplet” allgedly compromised for trivial, unpublicized website. Should I be worried abouty my own machine?

I got a message from D.O. about my Droplet saying they shut it down because there was a lot of outgoing traffic that looked like an attack. The site I had on that server was not very known at all. ...
0
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2answers
79 views

How can I block certain IP addresses from my router?

I have done some basic things protect my router like disabling wps setting strong passwords and stuff. However, I am using a virgin media superhub 2 where it does not seem to be possible to ssh into ...
0
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2answers
100 views

What are the risks associated with SSH'in from corporate LAN to untrusted server on the Internet

At work (a huge organisation) I found a server on the LAN that opens SFTP connections to 2 servers across the Internet. I assume the remote hosts are in the other parties DMZ. I know you are not ...
9
votes
4answers
6k views

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?
0
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1answer
60 views

SSH and shared secrets

There was a question on a quiz I took, about different authentication methods that SSH uses. The answers were combintions of the following four: username/password public key authentication shared ...
0
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0answers
27 views

How can I Run my Kali Tools on a Remote Server [migrated]

I am currently ssh-ed into a remote server. However, I do not have root permissions on the remote server and therefore am unable to install and use tools such as nmap. I've been trying to figure out ...
0
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0answers
71 views

Find the location of a hidden host

I'm doing a penetration test for a client who wants me to try and target a specific server. I have managed to get credentials(hard-coded in an in-house app) to a limited account on this server that ...
0
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2answers
70 views

Is Certificate-Based Authentication Really Better Than Password Authentication in OpenSSH?

I recently set myself up with a VPS and have been hardening it to the greatest extent of my limited knowledge! I was configuring OpenSSH to use certificate based authentication when something did not ...
2
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1answer
124 views

Key's random art image is mostly black

I have generated an SSH key on Ubuntu 10.04 with ssh-keygen -t rsa -C "example@example.com" and the key's random art image comes out mostly empty (modified slightly): +--[ RSA 2048]----+ | ...
1
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1answer
77 views

PCI DSS 3.0 - Is restricting SSH and/or RDP outbound required?

This question comes up a lot as I do evaluations for different customers. I currently recommend the following: All outbound SSH & RDP blocked by default from user network (non-CDE) All outbound ...
11
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2answers
619 views

What role does clock synchronization play in SSL communcation

We've recently implemented WS Trust security over SSL for our client / server communications. Our application is used by thousands of our customers, spread out all over the world. One of the ...
5
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2answers
209 views

SSH key auth, but still need password for sudo?

SSH with public-private key authentication comes enabled by default with most Linux distributions. This is great because when I create accounts for remote users I don't have to email them sensitive ...
2
votes
1answer
241 views

Bastion host that allows jailed users to SSH but protects private key

Basically, I'm trying to let the user use a private key without having read access to it. Use case: Employee needs to SSH to a server in the data center. There is 1 private key for all servers, ...
24
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2answers
2k views

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 ...
5
votes
1answer
95 views

What is the impact of RSA key's size on CPU load?

I use ssh connection encrypted and compressed. If I use small RSA keys or very big RSA keys, what is impact on CPU load for compression, for decompression and on bandwidth (encrypted file size) ?
4
votes
2answers
52 views

How to mitigate the risk of X forwarding?

I want to use X forwarding in my work because some tasks are just easier with GUI. I trust the administrators not to be malicious, but I don't trust their competence in security (almost nil). Hence ...
6
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2answers
6k 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 ...
0
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5answers
119 views

SSH server: What's more secure, pub key auth or Google Authenticator time-based auth?

I'm curious which would be more secure, pub key authentication or 2-factor auth via Google Authenticator. Apparently I can't use both. If I have pub key authentication, the Google Auth PAM module ...
2
votes
2answers
537 views

Pros/Cons to OpenVPN vs “VPN over OpenSSH”

What are the major differences between using OpenVPN and using VPN over OpenSSH? Does adding a virtual tunnel interface to a SSH connection offer the same benefits of OpenVPN? Can PuTTY be used on ...
0
votes
1answer
79 views

Shall I set “RSAAuthentication yes” in sshd_config if I use only ECDSA key?

In a context of proprietary client boxes and servers, I want to limit authentication to ECDSA keys. Historically, "RSAAuthentication yes" was used to enable authentication with RSA and maybe DSA keys. ...
2
votes
1answer
94 views

How does Putty derive the encryption key in its .ppk format?

I have been doing some reading on the mechanics of managing RSA key pairs, during which I learned that OpenSSL by default derives the encryption key by using MD5 on the passphrase (bad!) without any ...
2
votes
1answer
46 views

SSH key passphrase update and multiply locations

I have a ssh key which I use to upload code to github. the private key is located on several locations from where I upload/download data. I wonder how can I update (or expire) old keys after I update ...
0
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1answer
38 views

User-friendly public/private manual authentication protocol

I have a remote service which allows users to SSH login to the machine and they're automatically sent to the (command line) application (without access to a bash prompt, for instance). In the course ...
1
vote
1answer
35 views

Difference between sshv1 and 1.5?

I've been searching for the answer to this but haven't had much luck. What is the difference between SSH version 1 and 1.5? Is 1.5 a release of 1? As in 1.2, 1.3, 1.4, 1.5? Are there any ...
25
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3answers
2k views

Why is using SSH key more secure than using passwords?

If people use password to log in to a UNIX server, then it could be forced to expire the password, then they change it. If people use ssh key and have no passwords, no password expirity, then ...
0
votes
2answers
81 views

OTP vs. Keyfile

I have been wondering what are the benefits and cons of using an OTP (one time password) versus a keyfile to, for example, decrypt a keepass database, connect to a server via SSH, or other uses. ...
9
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2answers
5k 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 ...
0
votes
1answer
236 views

How compromised should I assume my computer is?

I had turned ssh on a while ago to do some remote work. I was just looking over some netstat info when I noticed someone had established an ssh session with me D: I turned ssh off immediately and ...
1
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0answers
41 views

NISTIR 7966 (Security of Automated Access Management Using Secure Shell) - is there anything new?

Tatu Ylönen (the creator of SSH protocol) and two others authored a report recently, offering their views on SSH key management. I have read the report, and am struggling to identify whether it is ...
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4answers
11k views

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 ...
6
votes
2answers
6k views

How does the ShellShock exploit work over OpenSSH?

The three options listed in the CERT release (AcceptEnv TERM and SSH_ORIGINAL_COMMAND) are all server-side options. If none of these are set on a host (and no http vector is available) is the host ...
0
votes
1answer
34 views

Period and direction of risk when connecting to malicious webserver

Please forgive my terminology mishaps. Recently, I tried to connect to a server over SFTP. The SSH public key response differed by 1 byte to what I was expecting, from an info page. I was tempted to ...
4
votes
1answer
91 views

Is limiting access to a web script with .htaccess secure enough when that script can run arbitrary commands?

Okay, so I don't have much HTML experience, but I recently started working on a project with a group of people that involves regularly manipulating files in a web server. I would like to work on this ...