<PAGE>

                                                            Exhibit 24


                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ William F. Aldinger

                                   -------------------------------
                                   William F. Aldinger
                                   Director


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
snder the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ Kenneth T. Derr

                                   -------------------------------
                                   Kenneth T. Derr
                                   Director


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                   /s/ M. Kathryn Eickoff-Smith
                                   -------------------------------
                                   M. Kathryn Eickhoff-Smith
                                   Director


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ Herbert L. Henkel

                                   -------------------------------
                                   Herbert L. Henkel
                                   Director


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ Frank C. Herringer

                                   -------------------------------
                                   Frank C. Herringer
                                   Director


<PAGE>


                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ Shirley Ann Jackson

                                   -------------------------------
                                   Shirley Ann Jackson
                                   Director


<PAGE>


                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /S/ Jon C. Madonna

                                   -------------------------------
                                   Jon C. Madonna
                                   Director


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ Donald F. McHenry

                                   -------------------------------
                                   Donald F. McHenry
                                   Director


<PAGE>


                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

      WHEREAS, AT&T CORP., a New York corporation (hereinafter referred to as
the "Company"), proposes to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, an
annual report on Form 10-K; and

      WHEREAS, the undersigned is a director of the Company:

      NOW, THEREFORE, the undersigned hereby constitutes and appoints R. S. FEIT
and CHRISTOPHER R. REIDY, and each of them, as attorneys for him or her and in
his or her name, place and stead, and in his or her capacity as a director of
the Company, to execute and file such annual report, and thereafter to execute
and file any amendment or amendments thereto, hereby giving and granting to said
attorneys, and each of them, full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises, as fully, to all intents and purposes, as he or she might or could
do if personally present at the doing thereof, hereby ratifying and confirming
all that said attorneys may or shall lawfully do, or cause to be done, by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
this 7th day of March, 2005.

                                    /s/ Tony L. White

                                   -------------------------------
                                   Tony L. White
                                   Director