Usually, simple SIM cards of the Kyivstar mobile operator, bought in some kind of stall or store, can be replaced independently with a new SIM card, for example, you can buy another SIM card there and call the operator, say that the old card is lost, report the last few dialed and accepted numbers, then the operator will block the old SIM card and activate a new one but with the same number that was on the old one.Continue reading ““Lock the self-replacement of SIM” at Kyivstar”
Once I had to remove from the blacklists IP addresses of different dedicated servers located in data centers, since some mail services did not receive emails from them, due to the fact that the previous tenant did not use the IP address honestly or had viruses, spammed, and the current one got locks.Continue reading “How to remove an IP address from email blacklists”
I will give an example of creating a bootable flash drive with Kali Linux.
Kali Linux is a security testing tool.
dhcdrop is a utility for suppressing unnecessary DHCP servers and stress testing.Continue reading “Suppression of DHCP servers (dhcdrop)”
I will give an example of setting up two-factor authentication in Nextcloud using Google Authenticator.Continue reading “Nextcloud two-factor authentication”
IPTables is a command line utility that is the standard interface for managing the firewall.Continue reading “How to configure IPTables”
I will give examples of viewing the number of active compounds:Continue reading “How to detect DDOS attacks”
I will give an example of a simple script against DDOS attacks for NAT servers.
The script is executed when the total number of “conntrack” connections is more than 500000, it saves to the text file the IP address which has the most “conntrack” connections, who has more than 10,000 – adds to the ipset list.
Suppose we have a signed SSL certificate, or we will receive it from Let’s Encrypt, as I described in this article:
Installing Certbot in Ubuntu
To install an SSL certificate for iRedMail, you need to specify it in the Dovecot, Postfix and Apache2 configuration.Continue reading “Install SSL Certificate for iRedMail”
I will give an example of setting up access by IP in nginx.
Suppose you use the standard nginx configuration file, open it in a text editor: