BPB Dirty Filter is a free tube distortion VST plugin by Bedroom Producers Blog.
https://bedroomproducersblog.com/free-vst-plugins/bpb-dirty-filter/
UPDATE: Some browsers and AV software are detecting the BPB Dirty Filter installer as a threat. It's a false positive and we have reported this to AV software providers. In the meanwhile, we added the manual installation files for Windows if you prefer that over using an EXE installer.