With Google's recent algorithmic updates heavily penalising dodgy backlinks, it's more important than ever to rid yourself of spammy traffic (a process that's now potentially far easier using Google's 'Disavow links' tool).
But first, of course, you need to locate the links themselves. Here's a list of options - both free and subscription-based - with which you can start to assess which sites are linking to yours.
Possibly one of the most comprehensive analytical tools out there, ahrefs bills itself as the "largest index of live links".
A free account gives 3 reports and 15 queries per day, but to access all its power you'll need to pay, with prices for premium accounts starting at $49/month for 20 reports and 500 queries per day.
A free service - and fairly impressive as such - analyzebacklinks provides you with a list of backlinks which you can export as a text file, and even allows you the option to reveal anchor text.
It's not going to be as comprehensive as major players such as ahrefs, above, but what do you expect for nothing?
Newish kid on the block backlinkfinder accesses Google's own backlist data - which is so scanty that it provides little real insight into the full extent of incoming links.
Nevertheless, the site also provides useful tidbits such as Pagerank, Bing and Yahoo Indexes, and, more interestingly perhaps, a link to Alexa's Linking In data, which often seems to turn up results other analysis misses.
Search engine blekko bills itself as 'the spam free search engine' - a swipe at its far bigger competitors. Whether it can establish itself as a serious search player remains to be seen, but its SEO options are certainly interesting.
Offering real-time information for a fairly hefty $99 a month, you can ruminate the pros and cons of signing up by viewing a live demo of the U.S. Whitehouse website's traffic (below). Fascinating stuff.
Open Site Explorer
Open Site Explorer allows you to pull up to 10,000 links. Basic linking information is free, (but it is pretty basic), whereas the Pro plan is free for 30 days and then $99 per month.