If your "security agent" is blocking TeXLive and you are not allowed to accommodate TeXLive (which could theoretically open doors to other untrusted programs or viruses), then TeXLive may still be run on your Windows machine using a couple of workaround approaches. They don't, however, fix the underlying cause of why you can't install TeXLive in the firstplace. So if you can't fix that conveniently, these will work:
One Approach: From TeXLive, download the full TeXLive Distribution ISO and "burn" that to DVD or external memory card, like a thumbdrive or SD card. ["burn" means you use special software to copy an iso, so that it's "binary" format stays intact. A regular "copy" will not work, as it rearranges the "bits" from one file format to the destinations file format]. So, this may also involve you downloading another app designed to "burn" iso files to their target destinations, unless you already have such a tool installed.]
Another Approach: [much more Laborious, put potentially more convenient after it's done] Use a Virtual Machine, with Linux running within, and TeXLive running within Linux... all on your Windows Machine.
[A virtual machine allows you to run an alternate operating system within Windows, but everything is "sandboxed" within the virtual machine, and software run within the virtual machine is isolated and kept from interfering with Windows operating system functions]
--Download a Virtual Machine like VirtualBox
--Download a Linux operating system like Ubuntu or Kubuntu (they install as iso files into the virtual machine as a later step)
--Install the virtual machine. With Virtualbox you will be warned that it will disrupt your network connections during the install. You can click NO if you want don't want to allow the VirtualBox a network connection, and then you can configure that later as desired, or use a manually downloaded texlive-full iso to install within the Virtual Box. ALSO make sure you serve 4GB or more RAM for Kubuntu (2GB minimum). Windows will be left with the remainder RAM reserved for itself (make sure it has at least an equal amount of RAM left).
-- click NEW from Virtualbox taskbar, and Create Virtual Machine select the operating system you want the Virtual Machine to Run As, NAME:whatever; TYPE:Linux; VERSION:Kubuntu. [at this point you will need to select your Ubuntu or Kubutu iso file from Virtualbox]
--If you setup the network connection, apply all updates to your Virtualbox Kubuntu operating system first, then with Kubuntu fully up-to-date, you can just open up the terminal-console window and issue this one command, which will download and install the full TeXLive distribution into VirtualBox. This command will work on Ubuntu or Kubuntu: sudo apt install texlive-full from the terminal window.
BUT, I hope you find a more convenient answer than that lengthy workaround.
Best Answer
I've been facing the same problem since TeX Live 2015 was released last month (I have Windows 7 Pro 64-bit OS). I've tried installing it every week (in the hopes that there is a bug, which will be fixed in the weekly updates) but no luck. I tried installing it from different mirrors but again no luck. Finally, I was able to figure out a workaround yesterday. Here's what I did:
This worked perfectly for me and TeX Live 2015 is up and running on my computer. Hope this solves your problem.