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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There might be a man in the middle attack against my server

I have a little $7.20/y VPS, and the fingerprint for the ECDSA key has changed three times on me. This time, it happened shortly after I reinstalled the server (same day, in fact.) I always disable ...
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2answers
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Should different versions of SSH give different VisualHostKeys?

I am SSHing to a server via Cygwin's SSH and via Ubuntu 14.04's SSH. Cygwin version: OpenSSH_7.1p2, OpenSSL 1.0.2e 3 Dec 2015 Ubuntu version: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.4, OpenSSL 1.0.1f 6 Jan ...
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1answer
47 views

Why OpenSSH deprecated DSA keys

There was a question RSA vs. DSA for SSH authentication keys asking which key is better. Basically all answers were more in a favour of RSA over DSA but didn't really tell that DSA would be somehow ...
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6answers
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Why is leaving a passworded SSH over the internet so bad?

I've heard multiple multiple times to never leave SSH with a password open over the internet. Why is this so bad? I understand the password can be bruteforced, but what if it is a very strong ...
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5answers
2k views

Should I use a second/dedicated IP address for SSH?

When running a public web server (e.g., with Apache), I've heard it's recommended to bind SSH to a second IP address, different from the one Apache is listening to. But for me it seems like this is ...
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3answers
148 views

How to (further) ensure SSH security?

I set up my Linux Ubuntu machine as an SSH server through no-ip.com and it works great. Recently I discovered the command, sudo lastb -ad -F -w which outputs a log of the most recent failed SSH ...
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5answers
100 views

Best Security Method for SSH Access

I have been starting to think about security in a bit more depth recently and have hit a few questions which I would really value opinions on. For years I have had the same SSH Keypair to get to my ...
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16 views

Establishing a ssh connection to a server behind a stateful firewall with reverse path [closed]

It has an iptables based stateful firewall with reverse path filtering (tight). All I need is to establish an ssh connection or any other file access port. The only port open to public is 80 and 443 ...
3
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1answer
33 views

How secure is GSSAPI single-signon over SSH?

I know it is possible to integrate Linux/SSH logins with a Windows AD by using GSSAPI (Kerberos) authentication instead of the classic ssh keys and/or passwords. However, I have been unable to find ...
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1answer
132 views

Blocking Chinese IP addresses

I recently checked one of my servers' auth.log file and noticed some very suspicious activity. I recently shut down my server's ssh daemon, so the logs end on Jan 22, but what I noticed after ...
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1answer
28 views

SSH “on keyboard interactive devices” brute force vulnerability

I was researching the OpenSSH brute force vulnerability "onkeyborad-interactive devices", however I am not sure how this command really works ssh -lusername -oKbdInteractiveDevices=`perl -e 'print ...
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2answers
73 views

Protecting account ssh keys from root

How can users ssh private keys be protected from root stealing and attempting to brute force them? I cannot use selinux as the vendor will not support the app when it's in use? Thanks
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8answers
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Am I experiencing a brute force attack?

When checking the auth log of a server with the command: grep sshd.\*Failed /var/log/auth.log | less I see thousands of lines like this: Jan 12 11:27:10 ubuntu-leno1 sshd[8423]: Failed ...
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2answers
4k views

How exploitable is the recent UseRoaming SSH problem?

I recently heard about a serious bug in an OpenSSH client (CVE-2016-0777 and CVE-2016-0778) that if I understood correctly could cause remote code execution. How difficult would be for an active ...
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1answer
21 views

Can a user verify the quality/safety of pregenerated SSH moduli parameters?

Many tutorials about how to mitigate the Logjam recommend regenerating Diffie-Hellman moduli. This is a resource intensive operation, especially for high-bit groups. This made me think if it made ...
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1answer
73 views

Will the result of HTTPS and SSH encryption of the same data be identical for two separate requests?

If I was to request an image over HTTPS and record the packets over WireShark and then inspect a peer's Wireshark and look for the same packets, would I be able to see if they requested the same file, ...
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1answer
35 views

ssh tunneling /port forwarding/access different subnet

Hi I need some good pointer or any recommendation any docs about this below stated scenario. During in my recent pentesting : My ip is 192.168.x.1(kali) By some how I managed to get root shell on ...
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1answer
59 views

Is it a breach to have a ssh program into a tomcat server

I start to working in a project here and find something that at least seems odd to me. Since I'm not an specialist I came here to ask. It is a Java Web project that was made to run into a Tomcat ...
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1answer
51 views

What is the benefit of an SSH tunnel vs a Netcat shell for remote communication?

On the (few) penetration tests that I've done so far, I've typically created a reverse shell with Netcat to run commands on the target machine. Now, it looks like a lot of people like to use an SSH ...
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3answers
208 views

vpn vs ssh, what to choose? [duplicate]

First of all i am noob in this area so came here to get some idea from the experts. My friend was telling me the other day that ssh is pretty secure protocol and one should not be worried about ...
3
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1answer
68 views

Security problems with password-less SSH

Is there any downside of configuring password-less SSH authentication? Although it is very handy and secure, if someone gets access to my system with my account and there is password-less ...
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0answers
72 views

is it possible Windows privilege escalation using freesshd keys? [closed]

I have unprivileged shell one system.By browsing all folder i found freeSSHD folder Directory of C:\Program Files\freeSSHd 09/26/2008 02:07 PM <DIR> . 09/26/2008 02:07 PM ...
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1answer
83 views

SSH Key vs Complex Password with Fail2Ban & Two Factor Authentication

Normally you hear that using an SSH Key is far more secure than using a regular password. However I've been wondering if this statement is really true. Let's say we have the following variables for ...
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2answers
42 views

What exactly does `ssh -T user@domain verify` do?

The example I'm specifically thinking of is: ssh -T git@github.com verify Looking at the docs (man ssh) I can see that -T is the flag to "Disable pseudo-terminal allocation", but what implications ...
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2answers
85 views

Choosing between SSH and HTTPS for executing script using McAfee ESM Nitro

We intend to use McAfee ESM Nitro (SIEM) for security monitoring of our infrastructure servers. To bring automation in system administration of our servers, we have developed some applications ...
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1answer
78 views

SSH ciphers, MAC and key-exchange (and pen-tests thereof)

At work we've been trying to move our external-facing services away from a policy of inclusivity (where we tried to accept as many people as possible) to a more security-focused setup. The first step ...
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1answer
48 views

SSH Access to Personal Server sudo vs su

I have a server running Debian, which is on the web, and has few traffic (I use it essentially for some coulds, calendars, etc. for me). In an attempt to secure its access, I made the following in the ...
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2answers
59 views

How much entropy should passphrases for encrypting ssh keys have?

When one generates keys using ssh-keygen one gets prompted for a passphrase to encrypt the generated key with. How strong should such a passphrase be, entropywise, to withstand a full-blown ...
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4answers
2k views

Is it safer to ssh as a privileged user than to ssh and sudo?

I came across this old paper, discussing the possibility of password length information being disclosed when usin SSH: Timing Analysis of Keystrokes and Timing Attacks on SSH. The paper has been ...
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3answers
152 views

What should I be aware of when opening my home server to the internet?

I've built a home server (pretty much just a basic PC with a couple of big HDDs) which I would like to use as an FTP server and a minecraft server. Both would be for members of my gaming community. I ...
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0answers
34 views

On the Import Client Key screen in Bitvise what is numeric field just next to the Location Profile dropdown?

What is this field for? I know I saved a profile in the beginning, and I want this private key to be attached to just the profile that I'm using, but what on earth is that numeric field for?
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61 views

SSH intrusion suspected: Logwatch report versus SSH log file entries

My Web server's Logwatch report shows ssh and su activity that should not be there: sshd: Sessions Opened: deployer: 45 Time(s) su: Sessions Opened: root -> deployer: 8 Time(s) ...
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33 views

Is CurveZMQ Mature Enough to be Trusted?

We're using ZMQ for our projects and are now looking at extending usage to traverse a LAN. We'd like to implement security as this LAN could potentially have hostile parties. I'm leaning towards ...
3
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1answer
61 views

Is the ssh-copy-id command secure?

I have 2 Ubuntu 14.04 servers with openssh-server installed on both. I've set up key-based authentication using RSA keys, without passphrase, so that I can run automated backup scripts, to a remote ...
2
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1answer
114 views

Is binding all private services to the 127.0.0.1 address and then accessing them via SSH using an RSA key pair of 4096 bits secure?

Is it secure to bind all private services only to the 127.0.0.1 address, and then use a local SSH client's local port forwarding with an RSA public / private key pair file of 4096 bits and a ...
3
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1answer
69 views

Does RekeyLimit property in sshd_config enforce re-keying / key re-exchange?

I have set the RekeyLimit property in sshd_config and tried to perform a SSH. However, I could not see rekeying happening in the verbose logs, all I see is the log message below at the start of the ...
4
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1answer
100 views

Likely Sources of MITM Attack over Public Internet SSH

Earlier today when attempting to ssh into my remote server, I got the standard man in the middle warning relating to inconsistent public keys. In fact the key-type wasn't even correct. My server uses ...
4
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2answers
84 views

Should I worry if I have tried to ssh into a 'fake' dyndns.org site? (with ssh keys)

I often ssh into servers for work and play using dynamic dns with ssh keys that are password protected. Twice now (shame on me!) I have mistyped the dyndns.org part of the address and been greeted ...
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1answer
62 views

SSH Server Authentication

I know this question was asked several times in several ways, for example: Can an SSH server fingerprint be spoofed? What stops an SSH server from MITMing logins? However, none provided the ...
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2answers
46 views

How do I know a new host key is safe to accept?

I am frequently rebuilding servers for staging and development. I connect to them with SSH for provisioning. In the process, I'll destroy a VM, rebuild it, and provision it all over again with the ...
13
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1answer
225 views

Yubikey / GPG with OpenSSH signed key

I am currently looking into the possibility of using Yubikey (NEO)'s to store the private SSH keys of my users. By searching the internet I've found several places that explain how you can generate a ...
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2answers
185 views

Docker X11 Forwarding Security

I am currently running a Docker container with a program with a GUI forwarded over SSH (using X forwarding over OpenSSH). The virtualized server has X11Forwarding enabled and I can connect to it from ...
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1answer
693 views

ssh signature question (no matching key exchange method found)

I recently followed the advice at this blog to tighten down my SSH security, which included restricting key exchange algorithms to ones not vulnerable to known (or assumed known) capabilities of Prime ...
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4answers
292 views

What are the advantages/disadvantages of changing the SSH/SFTP port in Linux?

I have setup a remote CentOS VM (through a host) for our websites. I read an online recommendation to change the default SFTP port from 22 to a higher port such as 22000. I understand it is security ...
3
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0answers
46 views

Wayland Partial Encryption for Mouse / Keyboard? (Also X and RDP)

Question What are the best practices for implementing Partial Encryption, to encrypt just the input devices (mouse/keyboard, etc), not the actual video display, during remote desktop sessions using ...
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1answer
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Does SSH use one pair of keys for encryption or two pairs of keys?

When SSH(OpenSSH) client connects to SSH server, then SSH server provides its public encryption key(for example /etc/ssh/ssh_host_rsa_key.pub) to SSH client so that SSH client can encrypt data sent to ...
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SSH attempt blocked now ECDSA keys changed

Last night I had an external IP tried to access my server over SSH. The attempt was blocked as it failed to authorise in the number of times and time limit that I'd specified. Doing a whois on the ip ...
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1answer
67 views

Generate RSA2 key in OpenSSH format in windows

I have to generate a key, RSA v2 in OpenSSH format. I am a bit confused. I am trying to generate it using Putty key generator. There I see an option SSH2-RSA and SSH1-RSA. So is SSH2-RSA the RSA2 key ...
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1answer
189 views

“Fix” man in the middle

I've just tried to ssh connect to a server (auth via ssh key), and get the well-known message WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!. I'm the server administrator (but I'm not really a good ...
6
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1answer
135 views

Does a VPN provide any security benefits over sshuttle or a vanilla ssh tunnel?

I use sshuttle to tunnel my traffic through one of my remote boxes whenever I'm in a cafe or connected to an insecure network. Does a VPN provide any additional security benefit over this kind of ...