Exhibit 10.1

LOAN MODIFICATION AGREEMENT

This Loan Modification Agreement (this “Loan Modification Agreement”) is dated
as of November 1, 2007, by and between SILICON VALLEY BANK, a California
corporation, with its principal place of business at 3003 Tasman Drive, Santa
Clara, California 95054 and with a loan production office located at One Newton
Executive Park, Suite 200, 2221 Washington Street, Newton, Massachusetts 02462
(“Bank”) and NETSCOUT SYSTEMS, INC., a Delaware corporation with offices at 310
Littleton Road, Westford, Massachusetts 01886-4105 (“Borrower”).

1. DESCRIPTION OF EXISTING INDEBTEDNESS AND OBLIGATIONS. Among other
indebtedness and obligations which may be owing by Borrower to Bank, Borrower is
indebted to Bank pursuant to a certain loan arrangement dated as of March 12,
1998, evidenced by, among other documents, a certain Amended and Restated Loan
and Security Agreement dated as of March 12, 1998 between Borrower and Bank, as
amended by certain Loan Modification Agreements between Borrower and Bank dated
March 11, 1999, March 10, 2000, June 27, 2000, March 9, 2001, August 14,
2001, September 7, 2001, March 10, 2002, November 7, 2002, March 19, 2003, dated
as of July 31, 2003, effective as of June 8, 2003, June 8, 2004, June 9, 2005,
and dated as of July 20, 2007, and effective as of June 5, 2007 (as may be
amended from time to time, the “Loan Agreement”). Capitalized terms used but not
otherwise defined herein shall have the same meaning as in the Loan Agreement.

Hereinafter, all indebtedness and obligations owing by Borrower to Bank shall be
referred to as the “Obligations”.

2. DESCRIPTION OF COLLATERAL. Repayment of the Obligations is secured by the
Collateral as described in the Loan Agreement, as modified hereby (the “Security
Documents”).

Hereinafter, the Security Documents, together with all other documents
evidencing or securing the Obligations shall be referred to as the “Existing
Loan Documents”.

3. DESCRIPTION OF CHANGE IN TERMS.

A. Modifications to Loan Agreement.

 

  1. The Loan Agreement shall be amended by deleting the following Section 2.1.2
entitled “Letters of Credit Sublimit” in its entirety:

“2.1.2 Letters of Credit Sublimit. If there is availability for Credit
Extensions under Section 2.1.1(a), Bank shall issue or have issued Letters of
Credit for Borrower’s account not exceeding (i) the Committed Revolving Line,
minus (ii) the outstanding principal balance of any Advances (including any Cash
Management Services), minus (iii) the FX Reserve, minus (iv) the amount of all
Letters of Credit (including drawn but unreimbursed Letters of Credit). The face
amount of outstanding Letters of Credit (including drawn but unreimbursed
Letters of Credit) may not exceed Ten Million Dollars ($10,000,000.00). Each
Letter of Credit shall be secured by cash on terms acceptable to Bank on and
after (i) the Revolving Maturity Date if the term of the Committed Revolving
Line is not extended by Bank, or (ii) the occurrence of an Event of

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Default hereunder. All Letters of Credit shall be, in form and substance,
acceptable to Bank in its sole discretion and shall be subject to the terms and
conditions of Bank’s form of standard Application and Letter of Credit
Agreement. Borrower agrees to execute any further documentation in connection
with the Letters of Credit as Bank may reasonably request. The obligation of
Borrower to immediately reimburse Bank for drawings made under Letters of Credit
shall be absolute, unconditional and irrevocable, and shall be performed
strictly in accordance with the terms of this Agreement and such Letters of
Credit, under all circumstances whatsoever.”

and inserting in lieu thereof the following:

“2.1.2 Letters of Credit Sublimit. If there is availability for Credit
Extensions under Section 2.1.1(a), Bank shall issue or have issued Letters of
Credit for Borrower’s account not exceeding (i) the Committed Revolving Line,
minus (ii) the outstanding principal balance of any Advances (including any Cash
Management Services), minus (iii) the FX Reserve, minus (iv) the amount of all
Letters of Credit (including drawn but unreimbursed Letters of Credit). The face
amount of outstanding Letters of Credit (including drawn but unreimbursed
Letters of Credit) may not exceed Five Million Dollars ($5,000,000.00). Each
Letter of Credit shall be secured by cash on terms acceptable to Bank on and
after (i) the Revolving Maturity Date if the term of the Committed Revolving
Line is not extended by Bank, or (ii) the occurrence of an Event of Default
hereunder. All Letters of Credit shall be, in form and substance, acceptable to
Bank in its sole discretion and shall be subject to the terms and conditions of
Bank’s form of standard Application and Letter of Credit Agreement. Borrower
agrees to execute any further documentation in connection with the Letters of
Credit as Bank may reasonably request. The obligation of Borrower to immediately
reimburse Bank for drawings made under Letters of Credit shall be absolute,
unconditional and irrevocable, and shall be performed strictly in accordance
with the terms of this Agreement and such Letters of Credit, under all
circumstances whatsoever.”

 

  2. The Loan Agreement shall be amended by deleting the following Section 2.1.3
entitled “Cash Management Service Sublimit” in its entirety:

“2.1.3 Cash Management Services Sublimit. Borrower may use up to Ten Million
Dollars ($10,000,000.00) for the Bank’s Cash Management Services (the “Cash
Management Services Sublimit”), which may include merchant services, direct
deposit of payroll, business credit card, and PC-ACH services identified in
various cash management services agreements related to such Cash Management
Services (the “Cash Management Services”). Such aggregate amounts utilized under
the Cash Management Services Sublimit shall at all times reduce the amount
otherwise available for Credit Extensions under the Committed Revolving Line.
Any amounts Bank pays on behalf of Borrower or any amounts that are not paid by
Borrower for any Cash Management Services will be treated as Advances under the
Committed Revolving Line and will accrue interest at the interest rate
applicable to Advances.”

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and inserting in lieu thereof the following:

“2.1.3 Cash Management Services Sublimit. Borrower may use up to Five Million
Dollars ($5,000,000.00) for the Bank’s Cash Management Services (the “Cash
Management Services Sublimit”), which may include merchant services, direct
deposit of payroll, business credit card, and PC-ACH services identified in
various cash management services agreements related to such Cash Management
Services (the “Cash Management Services”). Such aggregate amounts utilized under
the Cash Management Services Sublimit shall at all times reduce the amount
otherwise available for Credit Extensions under the Committed Revolving Line.
Any amounts Bank pays on behalf of Borrower or any amounts that are not paid by
Borrower for any Cash Management Services will be treated as Advances under the
Committed Revolving Line and will accrue interest at the interest rate
applicable to Advances.”

 

  3. The Loan Agreement shall be amended by deleting the following Section 2.1.4
entitled “Foreign Exchange Sublimit” in its entirety:

“2.1.4 Foreign Exchange Sublimit. If there is availability for Credit Extensions
under Section 2.1.1(a), then Borrower may enter into foreign exchange forward
contracts with the Bank under which Borrower commits to purchase from or sell to
Bank a set amount of foreign currency more than one business day after the
contract date (the “FX Forward Contract”). Bank shall subtract 10% of each
outstanding FX Forward Contract (the “FX Reserve”) from the foreign exchange
sublimit, which sublimit is a maximum of Ten Million Dollars ($10,000,000.00).
The total FX Forward Contracts at any one time may not exceed 10 times the
amount of the FX Reserve. Bank may terminate the FX Forward Contracts if an
Event of Default occurs.”

and inserting in lieu thereof the following:

“2.1.4 Foreign Exchange Sublimit. If there is availability for Credit Extensions
under Section 2.1.1(a), then Borrower may enter into foreign exchange forward
contracts with the Bank under which Borrower commits to purchase from or sell to
Bank a set amount of foreign currency more than one business day after the
contract date (the “FX Forward Contract”). Bank shall subtract 10% of each
outstanding FX Forward Contract (the “FX Reserve”) from the foreign exchange
sublimit, which sublimit is a maximum of Five Million Dollars ($5,000,000.00).
The total FX Forward Contracts at any one time may not exceed 10 times the
amount of the FX Reserve. Bank may terminate the FX Forward Contracts if an
Event of Default occurs.”

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  4. The Loan Agreement shall be amended by deleting Section 6.6 entitled
“Primary Accounts” and inserting the following new Section 6.6 entitled
“Accounts” in lieu thereof:

“6.6 Operating Accounts.

(a) Maintain its primary depository, and operating accounts with Bank.

(b) Provide Bank five (5) days prior written notice before establishing any
Collateral Account at or with any bank or financial institution other than Bank
or its Affiliates. In addition, for each Collateral Account that Borrower at any
time maintains, Borrower shall cause the applicable bank or financial
institution (other than Bank) at or with which any Collateral Account is
maintained to execute and deliver a Control Agreement or other appropriate
instrument with respect to such Collateral Account to perfect Bank’s Lien in
such Collateral Account in accordance with the terms hereunder, which Control
Agreement may not be terminated without the prior written consent of the Bank.
The provisions of the previous sentence shall not apply to deposit accounts
exclusively used for payroll, payroll taxes and other employee wage and benefit
payments to or for the benefit of Borrower’s employees and identified to Bank by
Borrower as such. The provisions of this Section 6 will not apply to accounts of
Borrower maintained with: (i) financial institutions outside of the United
States, and (ii) Chase Manhattan/Kaufman Brothers which funds shall be used
solely for the purpose of treasury stock re-purchases.”

 

  5. The Loan Agreement shall be amended by deleting Section 6.7 entitled
“Financial Covenants” in its entirety, and inserting in lieu thereof the
following:

“6.7 Financial Covenants. Borrower shall maintain at all times, to be tested as
of the last day of each month, unless otherwise noted:

(a) Liquidity. Beginning with the month ending September 30, 2007, and as of the
last day of each month thereafter, Borrower shall maintain Liquid Assets in an
amount equal to two (2) times the outstanding principal amount of the
Obligations of Borrower to the Bank, at any time. As used herein “Liquid Assets”
shall mean all unrestricted and unencumbered (without the written consent of
Bank) cash, Cash Equivalents, and marketable securities maintained at Bank or
SVB Securities (provided a control agreement is in place) in Borrower’s name and
not pledged to any other Person (without the written consent of Bank).”

 

  6. The Loan Agreement shall be amended by deleting the following definitions
appearing in Section 13.1 thereof:

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““Accounts” are all existing and later arising accounts, contract rights, and
other obligations owed to the Borrower in connection with its sale or lease of
goods (including licensing software and other technology) or provision of
services, all credit insurance, guaranties, other security and all merchandise
returned or reclaimed by the Borrower and the Borrower’s books and records
relating to any of the foregoing.

“Committed Revolving Line” means an Advance of up to $10,000,000.00.

and inserting in lieu thereof the following:

““Accounts” are all accounts as defined under the UCC, including all existing
and later arising accounts, contract rights, payment intangibles, and other
obligations owed to the Borrower in connection with its sale or lease of goods
(including licensing software and other technology) or provision of services,
all credit insurance, guaranties, other security and all merchandise returned or
reclaimed by the Borrower and the Borrower’s books and records relating to any
of the foregoing.

“Committed Revolving Line” means an Advance of up to $5,000,000.00.”

 

  7. The Loan Agreement shall be amended by inserting the following definitions
to appear alphabetically in Section 13.1 thereof:

“Cash Equivalents” means (i) marketable direct obligations issued or
unconditionally guaranteed by the United States or any agency or any State
thereof having maturities of not more than one (1) year from the date of
acquisition; (ii) commercial paper maturing no more than one (1) year after its
creation and having the highest rating from either Standard & Poor’s Ratings
Group or Moody’s Investors Service, Inc.; (iii) certificates of deposit issued
maturing no more than one (1) year after issue; and (iv) money market funds at
least ninety-five percent (95%) of the assets of which constitute Cash
Equivalents of the kinds described in clauses (i) through (iii) of this
definition.

“Collateral Account” is any Deposit Account or Securities Account.

“Control Agreement” is any control agreement entered into among the depository
institution at which Borrower maintains a Deposit Account or the securities
intermediary or commodity intermediary at which Borrower maintains a Securities
Account, Borrower, and Bank pursuant to which Bank obtains control (within the
meaning of the Code) over such Deposit Account or Securities Account.

“Deposit Account” shall have the meaning supplied to it in Section 9- 102 of the
Uniform Commercial Code.

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“Investment Property” shall have the meaning ascribed to it in Section 9-102 of
the Uniform Commercial Code, provided that Investment Property shall not include
equity interests in direct or indirect subsidiaries of Borrower.

“Proceeds” shall have the meaning ascribed to it in Section 9-102 of the Uniform
Commercial Code.

“Securities Account” shall have the meaning ascribed to it in Section 8- 501 of
the Uniform Commercial Code.”

 

  8. The Collateral description attached as Exhibit A to the Loan Agreement is
hereby replaced with the Collateral description attached as Exhibit A hereto.

 

  9. The Compliance Certificate attached as Exhibit C to the Loan Agreement is
hereby replaced with the Compliance Certificate attached as Exhibit B hereto.

4. FEES. Borrower shall pay to Bank a modification fee equal to Two Thousand
Five Hundred Dollars ($2,500.00), which fee shall be due on the date hereof and
shall be deemed fully earned as of the date hereof. Borrower shall also
reimburse Bank for all legal fees and expenses incurred in connection with this
amendment to the Existing Loan Documents.

5. CONSISTENT CHANGES. The Existing Loan Documents are hereby amended wherever
necessary to reflect the changes described above.

6. RATIFICATION OF LOAN DOCUMENTS. Borrower hereby ratifies, confirms, and
reaffirms all terms and conditions of all security or other collateral granted
to the Bank, and confirms that the indebtedness secured thereby includes,
without limitation, the Obligations.

7. NO DEFENSES OF BORROWER. Borrower hereby acknowledges and agrees that
Borrower has no offsets, defenses, claims, or counterclaims against Bank with
respect to the Obligations, or otherwise, and that if Borrower now has, or ever
did have, any offsets, defenses, claims, or counterclaims against Bank, whether
known or unknown, at law or in equity, all of them are hereby expressly WAIVED
and Borrower hereby RELEASES Bank from any liability thereunder.

8. CONTINUING VALIDITY. Borrower understands and agrees that in modifying the
existing Obligations, Bank is relying upon Borrower’s representations,
warranties, and agreements, as set forth in the Existing Loan Documents. Except
as expressly modified pursuant to this Loan Modification Agreement, the terms of
the Existing Loan Documents remain unchanged and in full force and effect.
Bank’s agreement to modifications to the existing Obligations pursuant to this
Loan Modification Agreement in no way shall obligate Bank to make any future
modifications to the Obligations. Nothing in this Loan Modification Agreement
shall constitute a satisfaction of the Obligations. It is the intention of Bank
and Borrower to retain as liable parties all makers of Existing Loan Documents,
unless the party is expressly released by Bank in writing. No maker will be
released by virtue of this Loan Modification Agreement.

9. COUNTERSIGNATURE. This Loan Modification Agreement shall become effective
only when it shall have been executed by Borrower and Bank.

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10. CONSENT TO ISSUANCE OF SENIOR SECURED FLOATING RATE NOTES. Bank hereby
consents (thereby waiving the restrictive covenants set forth in the Loan
Agreement) to (i) the issuance by Borrower of Borrower’s Senior Secured Floating
Rate Notes due 2012 (the “Borrower Notes”) pursuant to an indenture with Wells
Fargo Bank, National Association, as collateral agent (the “Note Collateral
Agent”), on behalf of the holders of the Borrower Notes, as may be amended from
time to time (the “Borrower Indenture”), (ii) the lien and security interest
created by the Security Agreement (as defined in the Borrower Indenture) on
substantially all of Borrower’s real and personal property and the real and
personal property of Borrower’s domestic subsidiaries, and (iii) the guaranty of
the Borrower Notes by Borrower’s domestic subsidiaries, and agrees that the
foregoing shall not constitute an “Event of Default” under the Loan Agreement.

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This Loan Modification Agreement is executed as a sealed instrument under the
laws of the Commonwealth of Massachusetts as of the date first written above.

 

BORROWER:     BANK: NETSCOUT SYSTEMS, INC.     SILICON VALLEY BANK By:  

/s/ David P. Sommers

    By:  

/s/ Robin Gill

Name:   David P. Sommers     Name:   Robin Gill Title:   Chief Financial Officer
and     Title:   Vice President   Senior Vice-President, General Operations    
 

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EXHIBIT A

The Collateral consists of all of Borrower’s right, title and interest in and to
the following personal property:

All Accounts, cash, Cash Equivalents, Deposit Accounts, Investment Property, and
Securities Accounts, whether now owned or hereafter acquired, wherever located
and all Proceeds and insurance proceeds of any or all of the foregoing.

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THE FOLLOWING EXHIBIT TO THE LOAN MODIFICATION AGREEMENT HAS BEEN OMITTED IN
ACCORDANCE WITH ITEM 601(B)(2) OF REGULATION S-K.

 

Exhibit B    Compliance Certificate

NetScout Systems, Inc. will furnish supplementally a copy of the omitted exhibit
to the Securities and Exchange Commission upon request, provided however that
NetScout Systems, Inc. may request confidential treatment pursuant to Rule 24b-2
of the Securities and Exchange Act of 1934, as amended for the exhibit so
furnished.