A credit default swap (CDS) is an instrument to transfer the credit risk of fixed income products. The buyer of a credit swap receives credit protection. The seller 'guarantees' the credit worthiness of the product. A protection buyer pays a periodic fee to a protection seller in exchange for a contingent payment by the seller upon a credit event (such as a default or failure to pay) happening in the reference entity. When a credit event is triggered, the protection seller either takes delivery of the defaulted bond for the par value (physical settlement) or pays the protection buyer the difference between the par value and recovery value of the bond (cash settlement). Simply, the risk of default is transferred from the holder of the fixed income security to the seller of the swap. For example, a mortgage bank, ABC may have its credit default swaps trading at 265 basis points (bps). It costs 265,000 euros to insure 10 million of its debt per year. A year before, the same CDS might have been trading at 7 bp , indicating that markets view ABC is facing a greater risk of default on its mortgage obligations.
Credit default swaps resemble an insurance policy, as they can be used by debt owners to hedge, or insure against credit events such as a default on a debt obligation. However, because there is no requirement to actually hold any asset or suffer a loss, credit default swaps can be used to speculate on changes in credit spread.
Credit default swaps are the most widely traded credit derivative product. The typical term of a credit default swap contract is five years, although being an over-the-counter derivative, credit default swaps of almost any maturity can be traded.
Warren Buffett famously described derivatives bought speculatively as "financial weapons of mass destruction." In Berkshire Hathaway's annual report to shareholders in 2002, he said "Unless derivatives contracts are collateralized or guaranteed, their ultimate value also depends on the creditworthiness of the counterparties to them. In the meantime, though, before a contract is settled, the counterparties record profits and losses -often huge in amount- in their current earnings statements without so much as a penny changing hands. The range of derivatives contracts is limited only by the imagination of man (or sometimes, so it seems, madmen)." The same report, however, also states that he uses derivatives to hedge, and that some of Berkshire Hathaway's subsidiaries have sold and currently sell derivatives with notional amounts in the tens of billions of dollars.

The market for credit derivatives is now so large, in many instances the amount of credit derivatives outstanding for an individual name are vastly greater than the bonds outstanding. For instance, company X may have $1 billion of outstanding debt and $10 billion of CDS contracts outstanding. If such a company were to default, and recovery is 40 cents on the dollar, then the loss to investors holding the bonds would be $600 million. However the loss to credit default swap sellers would be $6 billion. In addition to spreading risk, credit derivatives, in this case, also amplify it considerably.