Per default all configured properties are fulltext indexed if they are of type STRING and included in the node scope index. A node scope search finds normally all nodes of an index. That is, the select jcr:contains(., 'foo') returns all nodes that have a string property containing the word 'foo'. You can exclude explicitly a property from the node scope index:

<?xml version="1.0"?>

<!DOCTYPE configuration SYSTEM "http://www.exoplatform.org/dtd/indexing-configuration-1.0.dtd">

<configuration xmlns:nt="http://www.jcp.org/jcr/nt/1.0">

  <index-rule nodeType="nt:unstructured">

    <property nodeScopeIndex="false">Text</property>

  </index-rule>

</configuration>