Guide to the Secure Configuration of Debian 11

$ rpm -qVa

[xdmcp]
Enable=false

password requisite pam_cracklib.so try_first_pass retry=3

password required pam_cracklib.so try_first_pass retry=3 maxrepeat=3 minlen=14 dcredit=-1 ucredit=-1 ocredit=-1 lcredit=-1 difok=4

password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=

difok = 4
minlen = 14
dcredit = -1
ucredit = -1
lcredit = -1
ocredit = -1
maxrepeat = 3

$ sudo getent passwd | awk -F: '{ print $1}' | uniq -d

PASS_MAX_DAYS 

PASS_MIN_DAYS 

PASS_MIN_LEN 

PASS_WARN_AGE 

$ sudo awk -F: '!$2 {print $1}' /etc/shadow

$ sudo passwd [username]

$ sudo passwd -l [username]

$ sudo echo > /etc/securetty

ttyS0
ttyS1

vc/1
vc/2
vc/3
vc/4

# ls -ld DIR

PATH=:/bin
PATH=/bin:
PATH=/bin::/sbin

UMASK 

umask 

-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S umount -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S umount -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S umount2 -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S umount2 -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b32 -S umount2 -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=b64 -S umount2 -F auid>=1000 -F auid!=unset -F key=perm_mod

-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename,renameat -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename -S renameat -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S rename -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S rename -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S renameat -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S renameat -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S rmdir -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S rmdir -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S unlink -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S unlink -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S unlinkat -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=ARCH -S unlinkat -F auid>=1000 -F auid!=unset -F key=delete

-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b32 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=b64 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

-a always,exit -F arch=ARCH -S init_module,finit_module,delete_module -F key=modules

-a always,exit -F arch=ARCH -S delete_module -F key=modules

-a always,exit -F arch=ARCH -S finit_module -F key=modules

-a always,exit -F arch=ARCH -S finit_module -F key=modules

-a always,exit -F arch=ARCH -S init_module -F key=modules

-w /var/log/tallylog -p wa -k logins
-w  -p wa -k logins
-w /var/log/lastlog -p wa -k logins

-w /var/log/tallylog -p wa -k logins
-w  -p wa -k logins
-w /var/log/lastlog -p wa -k logins

-w  -p wa -k logins

-w  -p wa -k logins

-w /var/log/lastlog -p wa -k logins

-w /var/log/lastlog -p wa -k logins

-w /var/log/tallylog -p wa -k logins

-w /var/log/tallylog -p wa -k logins

-a always,exit -F path=/usr/sbin/init -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/init -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/poweroff -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/poweroff -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/reboot -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/reboot -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/shutdown -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F path=/usr/sbin/shutdown -F auid>=1000 -F auid!=unset -F key=privileged

findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid"

$ sudo find PARTITION -xdev -perm /6000 -type f 2>/dev/null

-a always,exit -F path=PROG_PATH -F perm=x -F auid>=1000 -F auid!=unset -F key=privileged

-a always,exit -F arch=b32 -S adjtimex -F key=audit_time_rules

-a always,exit -F arch=b64 -S adjtimex -F key=audit_time_rules

-a always,exit -F arch=b32 -S adjtimex -F key=audit_time_rules

-a always,exit -F arch=b64 -S adjtimex -F key=audit_time_rules

-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules

-a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -F key=time-change

-a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -F key=time-change

-a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -F key=time-change

-a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -F key=time-change

-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules

-a always,exit -F arch=b32 -S settimeofday -F key=audit_time_rules

-a always,exit -F arch=b64 -S settimeofday -F key=audit_time_rules

-a always,exit -F arch=b32 -S settimeofday -F key=audit_time_rules

-a always,exit -F arch=b64 -S settimeofday -F key=audit_time_rules

-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules

-a always,exit -F arch=b32 -S stime -F key=audit_time_rules

-a always,exit -F arch=b32 -S stime -F key=audit_time_rules

-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules

-w /etc/localtime -p wa -k audit_time_rules

-w /etc/localtime -p wa -k audit_time_rules

$ sudo systemctl enable ip6tables.service

$ sudo systemctl enable iptables.service

:INPUT DROP [0:0]

$ sudo service ip6tables reload

:INPUT DROP [0:0]

:FORWARD DROP [0:0]

-A INPUT -p icmp --icmp-type any -j ACCEPT

-A INPUT -p icmp --icmp-type echo-reply -j ACCEPT
-A INPUT -p icmp --icmp-type destination-unreachable -j ACCEPT
-A INPUT -p icmp --icmp-type time-exceeded -j ACCEPT

-A INPUT -p icmp --icmp-type echo-request -j ACCEPT

-A INPUT -p icmpv6 --icmpv6-type echo-request -j DROP

-A INPUT -p icmpv6 --icmpv6-type router-advertisement -j DROP

-A INPUT -s 10.0.0.0/8 -j LOG --log-prefix "IP DROP SPOOF A: "
-A INPUT -s 172.16.0.0/12 -j LOG --log-prefix "IP DROP SPOOF B: "
-A INPUT -s 192.168.0.0/16 -j LOG --log-prefix "IP DROP SPOOF C: "
-A INPUT -s 224.0.0.0/4 -j LOG --log-prefix "IP DROP MULTICAST D: "
-A INPUT -s 240.0.0.0/5 -j LOG --log-prefix "IP DROP SPOOF E: "
-A INPUT -d 127.0.0.0/8 -j LOG --log-prefix "IP DROP LOOPBACK: "

-A INPUT -i eth0 -s ::1 -j LOG --log-prefix "IPv6 DROP LOOPBACK: "
-A INPUT -s 2002:E000::/20 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "
-A INPUT -s 2002:7F00::/24 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "
-A INPUT -s 2002:0000::/24 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "
-A INPUT -s 2002:FF00::/24 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "
-A INPUT -s 2002:0A00::/24 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "
-A INPUT -s 2002:AC10::/28 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "
-A INPUT -s 2002:C0A8::/32 -j LOG --log-prefix "IPv6 6to4 TRAFFIC: "

-A INPUT -s FF05::/16 -j LOG --log-prefix "IPv6 SITE-LOCAL MULTICAST: "
-A INPUT -s ::0.0.0.0/96 -j LOG --log-prefix "IPv4 COMPATIBLE IPv6 ADDR: "

-A INPUT -d FF02::1 -j LOG --log-prefix "Link-local All-Nodes Multicast: "

-A INPUT -s ::0.0.0.0/104 -j LOG --log-prefix "IP NON-ROUTABLE ADDR: "
-A INPUT -s ::127.0.0.0/104 -j LOG --log-prefix "IP DROP LOOPBACK: "
-A INPUT -s ::224.0.0.0.0/100 -j LOG --log-prefix "IP DROP MULTICAST D: "
-A INPUT -s ::255.0.0.0/104 -j LOG --log-prefix "IP BROADCAST: "

-A INPUT -s ::FFFF:0.0.0.0/96 -j LOG --log-prefix "IPv4 MAPPED IPv6 ADDR: "
-A INPUT -s 2002::/16 -j LOG --log-prefix "IPv6 6to4 ADDR: "

-A INPUT -s FEC0::/10 -j LOG --log-prefix "SITE-LOCAL ADDRESS TRAFFIC: "

options ipv6 disable=1

net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

net.ipv6.conf.default.router_solicitations = 0
net.ipv6.conf.default.accept_ra_rtr_pref = 0
net.ipv6.conf.default.accept_ra_pinfo = 0
net.ipv6.conf.default.accept_ra_defrtr = 0
net.ipv6.conf.default.autoconf = 0
net.ipv6.conf.default.dad_transmits = 0
net.ipv6.conf.default.max_addresses = 1

$ sudo sysctl -w net.ipv4.conf.all.accept_local=0

net.ipv4.conf.all.accept_local = 0

$ sudo sysctl -w net.ipv4.conf.all.arp_filter=

net.ipv4.conf.all.arp_filter = 

$ sudo sysctl -w net.ipv4.conf.all.arp_ignore=

net.ipv4.conf.all.arp_ignore = 

$ sudo sysctl -w net.ipv4.conf.all.route_localnet=0

net.ipv4.conf.all.route_localnet = 0

$ sudo sysctl -w net.ipv4.conf.all.shared_media=

net.ipv4.conf.all.shared_media = 

$ sudo sysctl -w net.ipv4.conf.default.shared_media=

net.ipv4.conf.default.shared_media = 

$ sudo chgrp root /etc/group-

$ sudo chgrp shadow /etc/gshadow-

$ sudo chgrp root /etc/passwd-

$ sudo chgrp shadow /etc/shadow-

$ sudo chgrp root /etc/group

$ sudo chgrp shadow /etc/gshadow

$ sudo chgrp root /etc/passwd

$ sudo chgrp shadow /etc/shadow

$ sudo chown root /etc/group- 

$ sudo chown root /etc/gshadow- 

$ sudo chown root /etc/passwd- 

$ sudo chown root /etc/shadow- 

$ sudo chown root /etc/group