Although Mac OS has got an included firewall that only blocks incoming connections. There are commercial alternatives for that also block exfiltrating data : Little snitch and Handoff.
LuLu is the free, open-source macOS firewall that aims to block unknown outgoing connections, unless explicitly approved by the user.
Mainframes appeared in the early 1940s. The most popular suppliers are IBM, Amdahl, Hitachi, Bull, Nec, Tandem Computers. Although they can then be considered obsolete today, as in every decade since their creation, mainframe computers dominate the landscape of large-scale professional computing.
There are a few mainframe features that are common to all mainframe vendors: almost all mainframes have the ability to run (or host) multiple operating systems, can add or change hot disks without service interruption, are designed to manage very high-volume inputs and outputs, and focus on high-speed computing.
They are mainly used by large companies for critical applications requiring large volumes of data processing (a single mainframe can replace tens or even hundreds of smaller servers) in the banking, financial, healthcare, insurance, utilities, government and many other public and private companies, the mainframe continues to be the foundation of modern business activities.
The main difference between mainframes and supercomputers lies in their typical field of application – mainframes excel in reliable volume computing in areas requiring integer operations (e. g. Financial, indexing, comparisons, etc.). Supercomputers are designed to excel in their ability to perform floating point operations – addition, subtraction and multiplication with sufficient accuracy to model continuous phenomena such as weather conditions.
Despite the constant evolution of IT, mainframes are considered to be the most stable, secure and compatible of all IT platforms. The latest models can handle the most advanced and demanding customer workloads, while continuing to run applications written in previous decades.
Learning how to use a mainframe
Hercules
Hercules is a computer emulator that allows software written for IBM mainframes (System / 370, System / 390 and zSeries / System z) and compatible mainframes (such as Amdahl machines) to run on other types of hardware such as personal computers.
It runs on several parent operating systems, including GNU / Linux, Microsoft Windows, FreeBSD, Solaris and Mac OS X, and is marketed under the open source software license QPL. It is similar to Bochs and QEMU in that it only emulates instructions from the CPU and some devices. A supplier (or distributor) must always provide an operating system and the user must install it. Hercules was the first mainframe emulator to integrate support for IBM’s z-series.
IBM
With IBM online, by entering the “Master the Mainframe” contest organised by IBM to get free access to real IBM mainframes. First you will need to download and install a mainframe terminal emulator (for Windows, for Mac).