How to get rid of/permanently block a neighbor who is a cracker/"hacker?"

[mahesh]

Namaste' everyone,

I hope you all had a most excellent Mother's Day with really nice weather and cute critters running around outside.

I have an HP Stream which I just installed Ubuntu Budgie on yesterday. I have a parasite permanently residing and lurking on it who happens to be a guy who lives in the same building as I do. He apparently has some killer cracking/"hacking" skills and won't let up no matter how I have tried to block the usernames he's used. I have a suspicion he has some sort of backdoor app or something that lets him sneak in when I'm asleep or afk eating in the dining room or something.

I have tried installing different flavours of Linux to see if that wouldn't help; it didn't. I originally had Linux Mint, but also tried Zorin OS, and then this one that I'm using now.

I tried using the following command to see what he was up to (it worked but it still didn't get rid of him obviously):
sudo less /var/log/auth.log The most recent output of this command:

)
May 9 13:46:35 HP-Stream-Laptop-14-cb1xxx systemd-logind[577]: New session c2 of user rudrani1971.
May 9 13:46:35 HP-Stream-Laptop-14-cb1xxx systemd: pam_unix(systemd-user:session): session opened for user rudrani1971(uid=1000) by (uid=0)
May 9 13:46:35 HP-Stream-Laptop-14-cb1xxx lightdm: gkr-pam: gnome-keyring-daemon started properly and unlocked keyring
May 9 13:46:41 HP-Stream-Laptop-14-cb1xxx polkitd(authority=local): Registered Authentication Agent for unix-session:c2 (system bus name :1.79 [budgie-polkit-dialog], object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8)
May 9 14:01:29 HP-Stream-Laptop-14-cb1xxx lightdm: pam_unix(lightdm-greeter:session): session opened for user lightdm(uid=115) by (uid=0)
May 9 14:01:29 HP-Stream-Laptop-14-cb1xxx systemd-logind[577]: New session c3 of user lightdm.
May 9 14:01:29 HP-Stream-Laptop-14-cb1xxx systemd: pam_unix(systemd-user:session): session opened for user lightdm(uid=115) by (uid=0)
May 9 14:01:29 HP-Stream-Laptop-14-cb1xxx lightdm: gkr-pam: gnome-keyring-daemon started properly
May 9 14:01:30 HP-Stream-Laptop-14-cb1xxx lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "rudrani1971"
May 9 14:08:58 HP-Stream-Laptop-14-cb1xxx lightdm: gkr-pam: unable to locate daemon control file
May 9 14:08:58 HP-Stream-Laptop-14-cb1xxx lightdm: gkr-pam: stashed password to try later in open session
May 9 14:08:58 HP-Stream-Laptop-14-cb1xxx lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm
May 9 14:08:58 HP-Stream-Laptop-14-cb1xxx systemd-logind[577]: Removed session c3.
May 9 14:10:58 HP-Stream-Laptop-14-cb1xxx PackageKit: uid 1000 is trying to obtain org.freedesktop.packagekit.package-install auth (only_trusted:1)
May 9 14:11:07 HP-Stream-Laptop-14-cb1xxx polkitd(authority=local): Operator of unix-session:c2 successfully authenticated as unix-user:rudrani1971 to gain TEMPORARY authorization for action org.freedesktop.packagekit.package-install for system-bus-name::1.121 [/usr/bin/gnome-software --gapplication-service] (owned by unix-user:rudrani1971)
May 9 14:11:07 HP-Stream-Laptop-14-cb1xxx PackageKit: uid 1000 obtained auth for org.freedesktop.packagekit.package-install
May 9 14:13:20 HP-Stream-Laptop-14-cb1xxx sudo: rudrani1971 : TTY=pts/0 ; PWD=/home/rudrani1971 ; USER=root ; COMMAND=/usr/bin/less /var/log/auth.log
May 9 14:13:20 HP-Stream-Laptop-14-cb1xxx sudo: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=1000)
~
(END)

He (the cracker/"hacker") is the username lightdm. I'm rudrani1971. I'm running Ubuntu Budgie 22.04.

He keeps using something called "pam" which I'm working on figuring out, to break into my computer and rummage around; Gods only know what the hell he's doing.

Anything you folks can do to help me would be greatly appreciated. If there is something I have neglected to include in my information, please let me know and I'll see what I can do to supply it.

Thank you all for taking the time to read all this, and I look forward to your advice.