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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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 ...
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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 ...
5
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29 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
80 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 ...
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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 ...
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1answer
34 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 ...
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 ...
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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 ...
0
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2answers
80 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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1answer
62 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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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
125 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
vote
1answer
78 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
621 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
210 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 ...
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
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2answers
53 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 ...
0
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1answer
82 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. ...
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
1answer
95 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
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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 ...
3
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1answer
112 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 ...
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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 ...
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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 ...
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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. ...
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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 ...
9
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1answer
230 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 ...
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 ...
2
votes
2answers
550 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 ...
6
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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 ...
4
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1answer
93 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 ...
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75 views

Using SSH Private keys in Production environment

I have a need to scp a bunch of files from a production box to my development environment. I am a developer and have limited read access to the production machines. Instead of entering password for ...
0
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2answers
141 views

Why does ssh `known_hosts` file need server name?

When I push/pull repos on GitHub over SSH, sometimes there will a message about unidentified server and asks if I want to trust and add it to known_hosts. Apparently this is because GitHub has ...
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2answers
138 views

How common is port-knocking? [closed]

Today I read about port-knocking for the first time. It has been a pretty known concept for more than ten years, but I don't know anybody who uses it for their servers. How common is the usage of ...
7
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4answers
1k views

Why secure encrypted data consistency by strong hashing?

Consider the SSH protocol: the SSH packet is like [data, SHA1(data)]. The packet is entirely encrypted by a block cipher. The question is, why do we need a strong hash to protect the packet ...
0
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1answer
223 views

SFTP between guest virtual machine and its host

The System I am using Windows 7 host with Cygwin and a virtual machine running Linux. The actual running guest is an Arch Linux ISO. The Objective I want to share files between the Cygwin host and ...
2
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2answers
126 views

Receiving sensitive data uploaded on a Web server, and remotely accessing it without exposing it to theft

Edit: I mostly used my university's guidelines on how to meet DPA standards and their own. I extrapolated a bit because encryption on a VM hosted by my uni that is already probably encrypted makes ...
0
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2answers
183 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
58 views

Expiration / enforce change of passphrase for private ssh keys

Out of curiosity, and also to check whether this is doable at all: Is there any way using standard tools to assign an expiry date [only] to the passphrase of an ssh private key, or to enforce the ...
2
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7answers
360 views

Is it wrong to root login with SSH?

I've long been under the impression that with unix, you should never login as root. Now I've started using Virtual Private Servers over at DigitalOcean, and some advice is to use SSH keys to login as ...
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0answers
35 views

SSH web server good practises [duplicate]

Is it risky to open the SSH service on a web server (even with a strong password or with RSA keys) ? What are good practises to connect to a web server for maintenance ? Thank you !
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 ...
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2answers
143 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. ...
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0answers
93 views

Do SSH private keys always contain enough information to derive a public key?

I am working on a persistence model for SSH Private keys. The technology used is Java. Since the persistence structure of the public and private keys is pretty similar and using some of the Java APIs ...
0
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2answers
98 views

How to transfer securely a file between servers?

Let's say I have two Linux servers. One containing a desktop app database (running on a local network) and a webserver. I want to automatically transfer each hour a database file (with a size of a ...
0
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1answer
616 views

ssh always too many authentication failures

No matter on which server I try to connect via password login, I always get the error message Too many authentication failures for If I have exchanged the ssh-keys, I can login without password as ...
0
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1answer
110 views

Should I use the root account on my Digital Ocean server?

I have set up an SSH key with Digital Ocean that is automatically added to any servers I create. Is it okay to use this root account for SFTP and daily use or should I create another user account and ...