SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE TO

(Rule 14d-100)

Tender Offer Statement under

Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934

CYREN LTD.

(Name of Subject Company (Issuer))

WP XII INVESTMENTS B.V.

WP XII INVESTMENTS COÖPERATIEF U.A.

WARBURG PINCUS (CALLISTO) PRIVATE EQUITY XII (CAYMAN), L.P.

WARBURG PINCUS (EUROPA) PRIVATE EQUITY XII (CAYMAN), L.P.

WARBURG PINCUS (GANYMEDE) PRIVATE EQUITY XII (CAYMAN), L.P.

WARBURG PINCUS PRIVATE EQUITY XII-B (CAYMAN), L.P.

WARBURG PINCUS PRIVATE EQUITY XII-D (CAYMAN), L.P.

WARBURG PINCUS PRIVATE EQUITY XII-E (CAYMAN), L.P.

WARBURG PINCUS XII PARTNERS (CAYMAN), L.P.

WP XII PARTNERS (CAYMAN), L.P.

(Name of Filing Person (Offeror))

ORDINARY SHARES, NOMINAL VALUE NIS 0.15 PER SHARE

(Title of Class of Securities)

M26895108

(CUSIP Number of Class of Securities)

WP XII Investments B.V.

c/o Warburg Pincus LLC

450 Lexington Avenue

New York, NY 10017

Telephone: (212) 878-0600

(Name, address and telephone numbers of person authorized to receive

notices and communications on behalf of filing persons)

With copies to:

CALCULATION OF FILING FEE

Check the appropriate boxes below to designate any transaction to which the statement relates:

Check the following box if the filing is a final amendment reporting the results of the tender offer: ☐

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

This Tender Offer Statement on Schedule TO (this “Schedule TO”) is filed by WP XII Investments B.V., a private limited liability company organized under the laws of the Netherlands (“WP XII BV”), which is a wholly owned subsidiary of WP XII Investments Coöperatief U.A., a company incorporated in The Netherlands (“WP XII Investments Coöperatief”), which is jointly owned by (i) Warburg Pincus (Callisto) Private Equity XII (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII Callisto”), (ii) Warburg Pincus (Europa) Private Equity XII (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII Europa”), (iii) Warburg Pincus (Ganymede) Private Equity XII (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII Ganymede”), (iv) Warburg Pincus Private Equity XII-B (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII-B”), (v) Warburg Pincus Private Equity XII-D (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII-D”), (vi) Warburg Pincus Private Equity XII-E (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII-E”), (vii) Warburg Pincus XII Partners (Cayman), L.P., a Cayman Islands exempted limited partnership (“Warburg Pincus XII Partners”) and (viii) WP XII Partners (Cayman), L.P., a Cayman Islands exempted limited partnership (“WP XII Partners,” and together with WP XII Callisto, WP XII Europa, WP XII Ganymede, WP XII-B, WP XII-D, WP XII-E and Warburg Pincus XII Partners, the “WP XII Funds”; the WP XII Funds, collectively with WP XII BV and WP XII Investments Coöperatief, the “Bidder”), and relates to the offer by the Bidder to purchase 31,265,358 outstanding ordinary shares, nominal (par) value NIS 0.15 per share (the “Shares”), of Cyren Ltd. (“Cyren”), at $2.50 per Share, net to the seller in cash, less any applicable withholding taxes, and without interest, upon the terms of, and subject to the conditions to, the Offer to Purchase, dated November 20, 2017 (the “Offer to Purchase”), and the related Letter of Transmittal, copies of which are attached hereto as Exhibits (a)(1)(A) and (a)(1)(B), respectively (which, together with any amendments or supplements thereto, constitute the “Offer”).

This Schedule TO is intended to satisfy the reporting requirements of Rule 14d-1 under the Securities Exchange Act of 1934, as amended. Pursuant to General Instruction F to Schedule TO, the information contained in the Offer to Purchase and the Letter of Transmittal is incorporated herein by reference in response to all of the items of this Schedule TO as more particularly described below. Capitalized terms used herein but not otherwise defined have the meaning ascribed to such terms in the Offer to Purchase.

The information set forth under “Summary Term Sheet” in the Offer to Purchase is incorporated herein by reference.

(a) The information set forth in Section 8 (“Information Concerning Cyren”) of the Offer to Purchase is incorporated herein by reference.

(b) The information set forth under “Introduction” in the Offer to Purchase is incorporated herein by reference.

(c) The information set forth in Section 6 (“Price Range of the Shares Etc.”) in the Offer to Purchase is incorporated herein by reference.

(a), (b) and (c) The information set forth in the Offer to Purchase under “Introduction,” Section 9 (“Information Concerning the Offeror Group”) and in Schedule I to the Offer to Purchase is incorporated herein by reference.

(a) The information set forth in the following sections of the Offer to Purchase is incorporated herein by reference:

“Summary Term Sheet;”

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“Introduction;”

Section 1 (“Terms of the Offer; Proration; Expiration Date”);

Section 2 (“Acceptance for Payment and Payment”);

Section 3 (“Procedures for Tendering Shares or Notifying Us of Your Objection to the Offer”);

Section 4 (“Withdrawal Rights”);

Section 5 (“Certain Material U.S. Federal Income Tax and Israeli Income Tax Consequences”);

Section 11 (“Conditions to the Offer”); and

Section 14 (“Miscellaneous”).

The information set forth in the Letter of Transmittal and the Notice of Objection, copies of which are attached hereto as Exhibits (a)(1)(B) and (a)(1)(F), respectively, is also incorporated herein by reference.

(a) and (b) The information set forth in the Offer to Purchase under “Introduction,” “Background to the Offer —Interest of Persons in the Offer,” “Background to the Offer —Related Party Transactions,” Section 9 (“Information Concerning the Offeror Group”) and Schedule I to the Offer to Purchase is incorporated herein by reference.

(a) The information set forth in the Offer to Purchase under “Summary Term Sheet,” “Background to the Offer —Background” and “Background to the Offer — Purpose of the Offer; Reasons for the Offer” is incorporated herein by reference.

(c)(1) through (c)(7) The information set forth in the Offer to Purchase under “Background to the Offer — Plans for Cyren after the Offer; Certain Effects of the Offer,” Section 7 (“Effects of the Offer on the Market for Shares; Registration under the Exchange Act”) and Section 9 (“Information Concerning the Offeror Group”) is incorporated herein by reference.

(a), (b) and (d) The information set forth in the Offer to Purchase under “Summary Term Sheet,” “Background to the Offer — Background” and Section 10 (“Sources and Amount of Funds”) is incorporated herein by reference.

(a) and (b) The information set forth in the Offer to Purchase under “Introduction,” “Background to the Offer—Related Party Transactions,” Section 9 (“Information Concerning the Offeror Group”) and in Schedule I to the Offer to Purchase is incorporated herein by reference.

(a) The information set forth in the Offer to Purchase under Section 13 (“Fees and Expenses”) is incorporated herein by reference.

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(a) and (b) The information set forth in the Offer to Purchase under Section 10 (“Source and Amount of Funds”) is incorporated herein by reference.

(a) The information set forth in the Offer to Purchase under “Background to the Offer — Interest of Persons in the Offer,” “Background to the Offer — Related Party Transactions,” Section 7 (“Effects of the Offer on the Market for Shares; Registration Under the Exchange Act”), Section 9 (“Information Concerning the Offeror Group”) and Section 12 (“Legal Matters and Regulatory Approvals”) is incorporated herein by reference. The Bidder is not aware of any pending material legal proceedings relating to the Offer.

(c) The information set forth in the Offer to Purchase and the Letter of Transmittal is incorporated herein by reference.

On November 20, 2017, the Bidder issued a press release announcing the commencement of the Offer, a copy of which is filed as Exhibit (a)(5)(B) to this Schedule TO and is incorporated herein by reference.

Not applicable.

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SIGNATURES

After due inquiry and to the best of the knowledge and belief of the undersigned, the undersigned certify that the information set forth in this statement is true, complete and correct.

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Dated: November 20, 2017

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