Parameter manipulation in relation to Web services refers to the threat of an attacker altering the message payload in some way while the message request or response is in transit between the consumer and service.
To address this threat, you can digitally sign a SOAP message to allow the message recipient to cryptographically verify that the message has not been altered since it was signed. For more information, see the "Digitally Signing a SOAP Message" section in the WSE documentation.