/var/btmp with ssh:nottyroot

[Michael D. Setzer II]

Had one Fedora 32 machine that has the ssh port open.
the /var/btmp file was showing a number of lines with the ssh:nottyroot 
line followed by various different IP addresses.

Can stop the sshd service that the btmp file stops growing.

Use to use denyhosts on systems, but it seems to have been removed.
The old denyhost would add blocked ipaddresses to stop these sites?
Know that root is not allowed to login ssh by default, so are these lines 
just saying attempts had been blocked.

Have vsftpd setup to use passive ports, so blocking port 22 would not be 
a big deal. But just seeing the btmp file grow seems to show wasted 
bandwidth if not showing an issue.

Is it an issue or not??

Thanks.

+------------------------------------------------------------+
 Michael D. Setzer II - Computer Science Instructor (Retired)     
 mailto:[e-mail]                            
 mailto:[e-mail]
 Guam - Where America's Day Begins                        
 G4L Disk Imaging Project maintainer 
 http://sourceforge.net/projects/g4l/
+------------------------------------------------------------+

[stan]

On Sat, 26 Sep 2020 18:00:39 +1000
"Michael D. Setzer II via users"  wrote:
> Had one Fedora 32 machine that has the ssh port open.
> the /var/btmp file was showing a number of lines with the
> ssh:nottyroot line followed by various different IP addresses.
>
> Can stop the sshd service that the btmp file stops growing.
>
> Use to use denyhosts on systems, but it seems to have been removed.
> The old denyhost would add blocked ipaddresses to stop these sites?
> Know that root is not allowed to login ssh by default, so are these
> lines just saying attempts had been blocked.
>
> Have vsftpd setup to use passive ports, so blocking port 22 would not
> be a big deal. But just seeing the btmp file grow seems to show
> wasted bandwidth if not showing an issue.
>
> Is it an issue or not??

I think not, but am not sure, since my knowledge of this is limited.
I'm also not sure why denyhosts was dropped from Fedora, so it might be
meaningless to run it if it has been replaced by another mechanism
(systemd?), but you can go here,
https://koji.fedoraproject.org/koji/buildinfo?buildID=1130378
and download the F29 rpm and install it on your system.  The version
there is the same as the latest version from upstream,
https://sourceforge.net/projects/denyhosts/files/

It might be that the upstream project is not being developed anymore,
so it was dropped from Fedora, but it could also be that the package
maintainer orphaned it and no one picked it up.

The other possibilities are that fail2ban or tcp_wrappers might have a
means of doing what you want.  Someone else here might be able to
confirm or deny that.

[Jonathan Billings]

On Sep 26, 2020, at 04:01, Michael D. Setzer II via users  wrote:
> Use to use denyhosts on systems, but it seems to have been removed.
> The old denyhost would add blocked ipaddresses to stop these sites?
> Know that root is not allowed to login ssh by default, so are these lines 
> just saying attempts had been blocked.
>
> Have vsftpd setup to use passive ports, so blocking port 22 would not be 
> a big deal. But just seeing the btmp file grow seems to show wasted 
> bandwidth if not showing an issue.
>
> Is it an issue or not??

It means your ssh port is open and you are constantly being scanned, so blocking ssh from everywhere except trusted networks would be ideal.

DenyHosts used to just add to /etc/hosts.deny (hence the name) which isn’t used anymore by sshd.  It looks like it supports iptables too, but it’s better to use fail2ban, which supports firewalld, uses ipsets or nftables, and is considerably faster.  It supports reading the journal too so if you don’t want to use syslogd or send your log traffic off-host, it still works. Since you have vsftpd, it can also logs for it too.

--
Jonathan Billings

[Michael D. Setzer II]

On 26 Sep 2020 at 6:26, stan via users wrote:

Date sent:      	Sat, 26 Sep 2020 06:26:03 -0700
To:             	[e-mail]
Subject:        	Re: /var/btmp with ssh:nottyroot
Organization:   	zohofree
Send reply to:  	Community support for Fedora users 

From:           	stan via users 
Copies to:      	stan
> On Sat, 26 Sep 2020 18:00:39 +1000
> "Michael D. Setzer II via users"  wrote:
> > Had one Fedora 32 machine that has the ssh port open.
> > the /var/btmp file was showing a number of lines with the
> > ssh:nottyroot line followed by various different IP addresses.
> >
> > Can stop the sshd service that the btmp file stops growing.
> >
> > Use to use denyhosts on systems, but it seems to have been removed.
> > The old denyhost would add blocked ipaddresses to stop these sites?
> > Know that root is not allowed to login ssh by default, so are these
> > lines just saying attempts had been blocked.
> >
> > Have vsftpd setup to use passive ports, so blocking port 22 would not
> > be a big deal. But just seeing the btmp file grow seems to show
> > wasted bandwidth if not showing an issue.
> >
> > Is it an issue or not??
>
> I think not, but am not sure, since my knowledge of this is limited.
> I'm also not sure why denyhosts was dropped from Fedora, so it might be
> meaningless to run it if it has been replaced by another mechanism
> (systemd?), but you can go here,
> https://koji.fedoraproject.org/koji/buildinfo?buildID=1130378
> and download the F29 rpm and install it on your system.  The version
> there is the same as the latest version from upstream,
> https://sourceforge.net/projects/denyhosts/files/
>
> It might be that the upstream project is not being developed anymore,
> so it was dropped from Fedora, but it could also be that the package
> maintainer orphaned it and no one picked it up.
>
> The other possibilities are that fail2ban or tcp_wrappers might have a
> means of doing what you want.  Someone else here might be able to
> confirm or deny that.

Thanks for the reply. I did install the fail2ban and enabled it, but when I 
restarted the sshd I was seeing the same exact things in btmp. Ended up 
just blocking incoming port 22 on the router. Had 21 and 22 setup for ftp 
access, but since ftp has passive ports setup anyway, no need to have it 
open. Have 5 computers on home private network that can use port 22.

Usually use vnc to access machine, but Fedora has also just dropped 
vncserver program from latest update, and now wants to force running it 
via systemd?? Just downgrade to last version that worked, and blocked it 
from being updated at the moment..

Deny host was interesting, and you could check out the hosts.deny file 
and see what IPs where trying to break in. The /var/log/btmp file lists the 
stuff, but it isn't a text file, and shows repeated attempts.

Thanks again. Be Safe.
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+------------------------------------------------------------+
 Michael D. Setzer II - Computer Science Instructor (Retired)     
 mailto:[e-mail]                            
 mailto:[e-mail]
 Guam - Where America's Day Begins                        
 G4L Disk Imaging Project maintainer 
 http://sourceforge.net/projects/g4l/
+------------------------------------------------------------+

[Ed Greshko]

On 2020-09-27 06:52, Michael D. Setzer II via users wrote:
> The /var/log/btmp file lists the 
> stuff, but it isn't a text file, and shows repeated attempts.

The "lastb" command can be used to display the file in human readable form.