19. A system comprising: data processing apparatus comprising one or more processors; and a computer-readable medium storing computer software instructions executable by the data processing apparatus to perform operations comprising: determining a first frequency of occurrence of a phrase in a plurality of first text items describing business entities, wherein the first text items are received from a trusted source; determining a first ratio of the first frequency of occurrence to a count of the plurality of first text items by dividing the first frequency by the count of the plurality of first items; determining a second frequency of occurrence of the phrase in a plurality of second text items describing business entities, wherein the second text items are received from an untrusted source; determining a second ratio of the second frequency of occurrence to a count of the plurality of second text items by dividing the second frequency by the count of the plurality of second items; determining a likelihood that text items received from the untrusted source include spam; determining a likelihood that the phrase is spam based at least partially on the first ratio, the second ratio, and the likelihood that text items received from the untrusted source include spam; and determining a likelihood that a different text item received from the untrusted source and that includes the phrase is spam based at least in part on the likelihood that the phrase is spam.
19. A system comprising: data processing apparatus comprising one or more processors; and a computer-readable medium storing computer software instructions executable by the data processing apparatus to perform operations comprising: determining a first frequency of occurrence of a phrase in a plurality of first text items describing business entities, wherein the first text items are received from a trusted source; determining a first ratio of the first frequency of occurrence to a count of the plurality of first text items by dividing the first frequency by the count of the plurality of first items; determining a second frequency of occurrence of the phrase in a plurality of second text items describing business entities, wherein the second text items are received from an untrusted source; determining a second ratio of the second frequency of occurrence to a count of the plurality of second text items by dividing the second frequency by the count of the plurality of second items; determining a likelihood that text items received from the untrusted source include spam; determining a likelihood that the phrase is spam based at least partially on the first ratio, the second ratio, and the likelihood that text items received from the untrusted source include spam; and determining a likelihood that a different text item received from the untrusted source and that includes the phrase is spam based at least in part on the likelihood that the phrase is spam. 27. The system of claim 19 , wherein the plurality of first text items and the plurality of second text items represent attributes of business entities.