  Massive far-red and infrared imaging surveys in different bandpasses are the
main contributors to the discovery of brown dwarfs. The Virtual Observatory
represents an adequate framework to handle these vast datasets efficiently and
filter them out according to specific requirements. A statistically significant
number of BDs is mandatory for understanding their general properties better
for identifing peculiar objects. WISE, an all-sky survey in the mid-infrared,
provides an excellent opportunity to increase the number of BDs significantly,
in particular those at the lower end of the temperature scale. We aim to
demonstrate that VO tools are efficient in identifing and characterizing BDs by
cross-correlating public catalogues released by large surveys. Using VO tools
we performed a cross-match of the WISE Preliminary Release, the 2MASS Point
Source and the SDSS Data Release 7 catalogues over the whole area of sky that
they have in common ($\sim$ 4000 deg$^{2}$). Photometric and proper motion
criteria were used to obtain a list of BD candidates. A temperature estimate is
provided for each candidate based on their spectral energy distribution using
VOSA, a VO tool for SED fitting. We derive the spectral types from the
effective temperatures. Distances, calculated from the absolute magnitude-
spectral type relation, place our candidates at 14-80 pc from the Sun, assuming
that they are single. We have identified 31 BD candidates, 25 of which have
already been reported in the literature. The remaining six candidates have been
classified as L- (four) and T-type (two) objects. The high rate of recovery of
known BDs ($\sim$ 90% of the T dwarfs catalogued in 2MASS) demonstrates the
validity of our strategy to identify them with VO tools.
