Intellectual property protections for typefaces and fonts are questionable at best, though there are a few areas in which protections do hold, including Copyright, Design Rights (and Patents), and Trademark.1
Originally in the US and other jurisdictions, the idea of a typefaces is one which is pure utility (that is, smacking ink on paper, and conveying a glyph), and therefore there apparently was no art to it, no creation, and therefore no rights for copy protection.
This still holds today in terms of bitmapped fonts, which do not have anything unique about them. However, modern fonts are not bitmapped, but rather vectors (think svg rather than jpg/png/gif). And it turns out that there is some art to selecting vectors for a given typeface.
In a practical sense, however, making a new font out of an old one (that is, creating new vectors over a bitmap (not merely reverse engineering and copying the vectors in a given font), is not in violation of intellectual property law. Therefore look-alike fonts (done properly) are not illegal, and themselves are afforded the same protection (against copying the vectors or the fonts wholesale).
Design Patents and Design Rights
Some other kinds of intellectual property protections are awarded for design, in certain jurisdictions. In the US a Design Patent can be filed for fonts, and provides protection for 15 years (after 13 May 2015, previously it was 14 years). Microsoft generally files these, along with other larger companies, as patents are expensive to file and maintain.
In the UK there is a Design Right which provides 5 years of protection, and the ability to renew for 5 years, a total of 5 times, for up to 25 years of protection. This seems a stronger protection.
In the EU, there is a similar 5 year x 5 times design registration scheme. If designs are not registered, then they have an automatic 3 years of protection, which is non-renewable.
In Canada, fonts can be registered as a Design Patent with 5 years of protection, plus an additional 5 years extension possible.
In China, the law is quite muddled and cases are settled with conflicting interpretations, typefaces can be protected as computer programs, and as works of art.
Besides copyright and patent or design rights, there is also trademark, which is the name of the font or typeface. This protection means that look-alike fonts, while legal, must not infringe trademark rights (have the same or a derrived name). URW++ fonts got into trouble by simply prepending URW