Password dictionary attack, all words in one or more dictionaries are tested. Lists of common passwords are also typically tested. Password strength is the likelihood that a password cannot be guessed or discovered, and varies with the attack algorithm used. Cryptologists and computer scientists often refer to the strength or 'hardness' in terms of entropy. Passwords easily discovered are termed "weak" or "vulnerable"; passwords very difficult or impossible to discover are considered "strong". There are several programs available for password attack (or even auditing and recovery by systems personnel) such as L0phtCrack, John the Ripper, and Cain; some of which use
Most recent common ancestor Most recent common ancestor In biology and genealogy, the most recent common ancestor (MRCA, also last common ancestor (LCA), or concestor) of any set of organisms is the most recent individual from which all the organisms are directly descended. The term is also used in reference to the ancestry of groups of genes (haplotypes) rather than organisms. The MRCA of a set of individuals can sometimes be determined by referring to an established pedigree. However, in general, it is impossible to identify the exact MRCA of a large set of individuals, but an estimate of the time at which the