Wow, this is some scary stuff - it is legible Russian text! But, it is not font manipulation, it is actual text replacement that you are observing.
The only thing that comes to mind is that you have some automatic translation software installed, which tries to translate some (but apparently, not all) English words and phrases into almost correct Russian counterparts. Google Chrome has a setting to automatically translate web pages. If you are seeing this only in Chrome, that must be it.
If you are seeing it in other desktop applications like Thunderbird, it may be some other desktop translation software like AthHek Google Translate Desktop or ABBYY Lingvo. Finally, it may be a virus, but this is not very likely due to complexity of the effort needed.
1What makes you think they are Russian? If it is really Russian, it is legible Russian text (if you know Russian, that is) or is it simply junk text using Cyrillic characters? – mvp – 2013-10-05T20:30:04.700
I have attached your question to show the problem. Can you help with this issue? I have run Norton in addition to McAfee and Malwarebytes, but no issues were found.
What makes you думать they есть Russian? If it is на самом деле Russian, it is legible Русский язык text (if you know Russian, that is) or is it simply junk текст using Кириллицей characters? – joanna – 2013-10-05T23:51:08.267
I have a hunch what it might be, but the raw text isn’t good enough, take a screenshot of an example and add it to the question. Also, what do you mean by your “email”? Do you mean an email client program or web-mail (in your browser)? – Synetech – 2013-10-06T00:44:12.430