7. A data processing apparatus, comprising: a scanner for receiving an electronically parseable document, and for scanning the document according to at least one predefined rule to determine if the document is suspicious; a first parser for parsing the document if the document is determined not to be suspicious; and a second parser for parsing the document if the document is determined to be suspicious, wherein the scanner is adapted to determine if the document is suspicious before passing the document to one of the first parser or the second parser, wherein if the document is determined to be suspicious, the document is passed from the scanner to the second parser without first passing the document from the scanner to the first parser, wherein the document is determined to be suspicious if the document includes a property that may cause a receiving computer system to fail, wherein the document is determined to be suspicious if the document comprises a well-formed document within a plurality of rules, but when the document is parsed, the document fails or slows down the receiving computer system to fail, and wherein the property includes at least one of a length of an attribute name, a number of an attribute per element, and a number of nested elements that exceeds a predetermined threshold.
7. A data processing apparatus, comprising: a scanner for receiving an electronically parseable document, and for scanning the document according to at least one predefined rule to determine if the document is suspicious; a first parser for parsing the document if the document is determined not to be suspicious; and a second parser for parsing the document if the document is determined to be suspicious, wherein the scanner is adapted to determine if the document is suspicious before passing the document to one of the first parser or the second parser, wherein if the document is determined to be suspicious, the document is passed from the scanner to the second parser without first passing the document from the scanner to the first parser, wherein the document is determined to be suspicious if the document includes a property that may cause a receiving computer system to fail, wherein the document is determined to be suspicious if the document comprises a well-formed document within a plurality of rules, but when the document is parsed, the document fails or slows down the receiving computer system to fail, and wherein the property includes at least one of a length of an attribute name, a number of an attribute per element, and a number of nested elements that exceeds a predetermined threshold. 11. The apparatus according to claim 7 , being designed to monitor a performance of the first parser and to create a new rule in dependence on the monitoring.