<PAGE>

                                                                      Exhibit 5


                               Hale and Dorr LLP
                              Counsellors at Law
                 60 State Street, Boston, Massachusetts 02109
                        617-526-6000 * FAX 617-526-5000


                               November 12, 1999


Be Free, Inc.
154 Crane Meadow Road
Marlborough, MA 01752

         Re:  Registration Statement on Form S-8
              ----------------------------------

Ladies and Gentlemen:

         This opinion is furnished to you in connection with a Registration
Statement on Form S-8 (the "Registration Statement") filed with the Securities
and Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended (the "Securities Act"), for the registration of 212,500 shares of
Common Stock, $.01 par value per share (the "Shares"), of Be Free, Inc., a
Delaware corporation (the "Company"), issuable under the Company's 1999 Employee
Stock Purchase Plan (the "Plan").

         We have examined the Certificate of Incorporation and By-Laws of the
Company, each as amended and restated to date, and originals, or copies
certified to our satisfaction, of all pertinent records of the meetings of the
directors and stockholders of the Company, the Registration Statement and such
other documents relating to the Company as we have deemed material for the
purposes of this opinion.

         In examination of the foregoing documents, we have assumed the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals, the conformity to original documents of all documents submitted to
us as copies, the authenticity of the originals of such latter documents and the
legal competence of all signatories to such documents.

         We express no opinion herein as to the laws of any state or
jurisdiction other than the state laws of the Commonwealth of Massachusetts, the
Delaware General Corporation Law statute and the federal laws of the United
States of America.
<PAGE>

         Based upon and subject to the foregoing, we are of the opinion that the
Shares have been duly authorized for issuance and the Shares, when issued and
paid for in accordance with the terms of the Plan, will be validly issued, fully
paid and nonassessable.

         It is understood that this opinion is to be used only in connection
with the offer and sale of the Shares while the Registration Statement is in
effect.

         Please note that we are opining only as to the matters expressly set
forth herein, and no opinion should be inferred as to any other matters.

         We hereby consent to the filing of this opinion with the Commission as
an exhibit to the Registration Statement in accordance with the requirements of
Item 601(b)(5) of Regulation S-K under the Securities Act. In giving such
consent, we do not hereby admit that we are in the category of persons whose
consent is required under Section 7 of the Securities Act or the rules and
regulations of the Commission.

                                                     Very truly yours,



                                                     /s/ HALE AND DORR LLP