<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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                        /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,
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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                    /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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                       /s/  M. Kathryn Eickhoff
                                       ---------------------------
                                       M. Kathryn Eickhoff
                                       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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                        /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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                      /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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                          /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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                         /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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                     /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 N.S. CYPRUS 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
amendments 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 12th day of March, 2004.

                                       /s/  Tony L. White
                                       ---------------------------
                                       Tony L. White
                                       Director